Let me make sure I understand what you're putting out here.
Google's web site, YouTube, which they have demonstrably gimped in Firefox at times, has a slightly nicer "window to full screen" transition in Chrome (a Google browser) than Firefox.
I just compared it on Windows (Core i5 13400 64GB, AMD 6600, 1080p) in FF versus Chrome and the transition is.... I don't know, a hair faster on Chrome? I don't even know what is "janky" about the Firefox version. I might even say it looks a little nicer in Firefox because of that fade.
If I was to describe what I'm feeling right now, I think "exasperation" would be the closest word but that doesn't really begin to describe how frustrating that sort of "evidence" for Chrome's superiority is.
I don't have a Linux desktop environment at the moment to compare the rest.