One of the reasons iOS feels smoother than Android is because the render loop of the OS is decoupled from the app. The apps aren’t allowed to introduce jank, so if you’re scrolling a webpage and stuff is loading simultaneously, iOS will be way smoother. I think this is also why they can have such low latency on inputs, for example with the Apple Pencil which is much lower latency than the surface pen or the android stylus. I had a 120hz android phone for over a year, and while the frame rate when scrolling is slightly worse on iOS, overall the OS feels more fluid to me. On a 120hz iPad it’s no comparison.

I am speculating here as I don’t know for sure, but I remember iOS started as a derivation of OSX so this may be the case for macOS as well. So I think it’s not your imagination, it’s a different input and render architecture than windows or android.