I was a theme junkie back in Windows 98 times, but stopped bothering since it became increasingly clear that Microsoft was not really interested in supporting them after XP.
The underlying problem is Chrome exposes no (normal) setting to override the OS level setting at all, not necessarily that the preference shall always follow the browser's theme specifically.
So if the user sets dark mode in the browser, do they not explicitly express their preference for websites? How could they be more explicit about the setting?
[1]https://drafts.csswg.org/mediaqueries-5/#prefers-color-schem...
Chrome already has a setting to change a specific website's color-scheme, although it's only working when Developer Tools is visible (then with Cmd+Shift+P "Toggle CSS media feature prefers-color-scheme"), so CSS implementation actually follows respecting UA-level preference over OS-level setting.
But again, Chrome doesn't have a feature that lets users to choose which color-scheme they want to browse the web (so there is no bug, but it's a UX issue because their Appearance settings doesn't make it clear to the users what this setting changes) other than the setting they gave to developers. Honestly I would love to see all browsers have an option for how color-scheme settings should apply to websites.
However, your original comment was saying that prefers-color-scheme is bugged in Chrome is not true. It works as intended: it follows both UA-level and OS-level settings correctly.
The settings in Appearance tab is not a setting for preference when browsing the web. Many apps have a setting to choose if their app should change appearance when OS setting changed (or to override it), they could simply leave out this setting and let Chrome chrome (app ui) always follow the OS setting or always be in default light mode, instead they gave users to choose "how their Chrome browser will look like", not "how every website they visit should look like".
Safari and Firefox are pretty small.
- <meta name="color-scheme" content="light dark">
- :root { color-scheme: light dark }
- @media (prefers-color-scheme: dark) { }
- <picture><source media="(prefers-color-scheme: dark)">
Did they not look at the prior art and notice that "one of these things is not like the other?" All the other pieces of this puzzle, conceivably, could have one day had something like `:root { color-scheme: halloween }` or `@media (prefers-color-scheme: supercontrast)` but no, we're just going to cement `light-dark()` as the only two possible color schemes we'd ever want to switch between forever.
Also, prefers-contrast media query exists, which can be used in combination with the luminance modes (color-scheme): halloween-light, halloween-dark, halloween-light-high-contrast, halloween-dark-high-contrast.