Otherwise you get Internet Explorer, in reverse: https://www.quirksmode.org/blog/archives/2021/08/breaking_th...
Chrome literally doesn't even bother pretending that many of their proposals are more than some scribbles in spec-adjacent format. E.g. a spec for WebHID that other browsers could implement was just dumped into the repo after Chrome shipped it.
Constructable Stylesheets had both a badly named API and a trivially triggered race condition. Shipped in Chrome in the middle of discussion because Google-developed lit "needed" it.
And so on and so forth.