Summary: In certain circumstances webview rendering is slow because it has to integrate with the android rendering API incase an app wishes to synchronize some App UI with web UI.
This isn't a limitation in chrome itself, which means chrome rendering has better performance for these specific operations (animations mostly).
Personally I think the chrome rendering path should always be used, and apps which want to draw under/over web content will have to deal with a frame or two of delay.
To save you having to read a really long comment thread: https://engineering.fb.com/2022/09/30/android/launching-a-ne...
Basically, FB's engineering replaced it with a full chromium based webview and explained the reasons android webview sucks ass.
How about they let us opt out of using it at all and just let us use our own browser?
unfortunately nobody cares :(
It's amazing bugs like this persist, even with the significant resources of several megacorps allocating legions of full-time developers to the codebase.