Nobody expects the scroll behavior to be different on a webpage, so it's always a surprise when a page does something like this. Then, you have to learn to adapt to how it expects you to scroll so that you don't screw up its animations or overshoot.

It's the kind of UI that works if you scroll a specific way. A lot of people probably do. But if you don't, it's all very tedious. I consider that to be poor design.

It ignores my scroll wheel most of the time if I try to scroll multiple times in a row.

The scroll is delayed significantly from when I scroll to when it actually scrolls.

The amount scrolled is inconsistent, sometimes it scrolls a very slowly a tiny amount because the page doesn't fit on the screen by an unknown tiny fraction, but if I scroll again because it is scrolling both slowly and with delay it now scrolls an entire page.

If I want to scroll past one of the demos I have to wait

If I drag the scroll bar on the side slightly it often snaps backwards.

It feels like I'm interacting with a phone/tablet screen on a computer, there's a reason why windows 8 failed.

It just violates my expectations, and thus feels frustrating. And there's almost no benefit.

It would be like if my shoes suddenly made me take steps at perfect widths, and no matter how/where I tried to step on my own, they forcibly move my foot to the spot they think is best. Like, okay, I see the good intentions here. But I have no trouble walking on my own. I don't need help. So I'm not sure what problem this solves. And this would obviously feel jarring and awkward, and would take a lot of getting used to until it didn't.

Except at least my shoes go with me, so presumably if I had a pair of auto-stepping shoes I would get used to them over time. But this website is a one-off, I'm going to visit once and never again, so it's just going to be weird and jarring, and then I'll leave.

For me, I scrolled, clicked, but the page hijacked my screen, moved its position by force, and I was not certain which pane I was on immediately. It broke my sense of continuity.

I am only being literal when I say this, but as someone who is actively keeping an eye out for this sort of thing (CSS frameworks, UI kits), I lost interest pretty immediately when I saw that and closed the tab immediately. Assuming the people who made this page also made the UI kit, it tells me their web design values run contrary to mine.

I don't even fall into one of the exceptional cases, and this was a very bad using-a-website experience for me.

It's completely broken if you use it with a mouse that has a scrollwheel.

In my case it's way too sensitive, causing me to scroll too far every time.

Navigating by clicking and holding a desired position on the scrollbar is completely broken.

Some of the "slides" have more content than fits vertically in the viewport, and trying to scroll to the bottom to see it without getting bounced to the next slide or back to the top is very touchy and tedious.

It is bad because you are deciding something for ME, the user. That's bad UX because I want to decide my own experience and scroll jacking is the worst thing you can do for UX. Stop doing this.

I’m on my phone and scrolling this page just leads to it constantly jumping up and down and makes it difficult to read as nothing stays in one place if I scroll a little bit.

Different browsers handle scrolling differently, and people use a myriad of different "pointer" input devices, there's too many permutations to handle correctly. It's for similar reasons why building native inputs from scratch are fraught with peril (see this item from a few days ago)

https://news.ycombinator.com/item?id=48930136

On a desktop or laptop computer, most trackpads have an immediate response curve. I am using one now, an Apple Wireless Trackpad. A very large amount of engineering effort over decades of time and millions of lifetime hours went into making it behave that way over a common wireless medium. I scroll a little bit, it scrolls a little bit, immediately, I scroll a lot, it scrolls a lot, immediately, and if I flick my finger from the bottom to the top and let go, it behaves as if I swiped a page of paper on my desk in the same fashion, with inertia taking over, proportional to how fast I flicked.

There is therefore an intrinsic physical link between the actions of my fingers, and the motion on the web page. My finger moves, and an immediate, proportional response is observed. This is an utterly base level of how most humans interact with the world. It is why using a mouse or trackpad came quite easy to many people (and why some can flick a mouse in a shooter, turn a precise 274.9 degrees, move up 14.2 degrees, and click on the head of an enemy player in fractions of a second with pinpoint accuracy). It is also why even a toddler can use a touchscreen; direct manipulation is inherently understandable to even a baby.

When I am turning in a screw by hand with a screwdriver, the feeling of the screws threads through the handle into my fingers, the immediate force feedback, the observable, feelable progress of the screw in or out of its screwhole, forms this same interface. Where human and tool meet, latency and unexpected behavior, especially if divorced from the input force, are undesirable qualities of a tool.

Scroll jacking is to a trackpad or a fine scroll wheel as turning a screwdriver handle by twisting a bungee cord is to using a screwdriver. It unhooks the immediate, direct feedback from the motion of my hand; its jarring, unpleasant, frustrating. On this page, I immediately put two fingers on the trackpad and moved them less than a centimeter, and didnt let go, and the entire screen cycled its view, as if I pressed a button "move to next item". Except I didn't (and why would I want that in the first place???), I just moved my fingers less than a centimeter. Nothing in the real world moves like that except for things less than a centimeter away from falling out of balance. And it feels the same. Precarious. A common human reaction to things moving out of proportion to our body is nausea!

I think a better question is, can you give an example of "why/how" this solves any actual problem someone would have had scrolling this website had it not used scroll snapping? Would the top comment have been "Boy I wish this site had used scroll snapping, it would have been more well done and enjoyable that way"?