Yes, and both Windows and MacOS have features to put things side by side... but they're not very intuitive and may require multiple inputs to achieve what the browser(s) do with one or two presses. On MacOS you have to long-press the "maximize" button, for example. I forgot that was a thing before reading this actually, but then I use the third-party tool Rectangle for window management.

Sure, but this is a lot nicer because when they are separate windows, and you have more windows, and if you have to alt-tab to check something else, it is a bit flow-breaking to bring these exact two windows back on top.

Yes, but they are grouped under one single tab, so for me at least is more easy to alt-tab to other app and return to the split view.