Even just the WebKit commits with Apple engineering contacts is enough to build a whole company around...
A lot of times, you can end up with amazing new ideas that way, but sometimes a change based on ego / "that person is just so brilliant" is just bad. The tab bar thing is going to be Touch Bar 2.0, I think.
The question is, how long is Apple going to push it? I was hopeful the Touch Bar would die with M1 Macs...
I doubt Apple's inner workings are simplistic in such a way that one person with some sort of clout pushed this with no further thought.
At the end of the day this is just speculation but purely negative speculation is just some form of populism/FUD and makes everything worse.