Apple's human interface guidelines says that some things can be written down though. It's a very thurough look at UX and while they don't adhere to them perfectly themselves, it's very much a north star to a some ideals. You can't unit test for taste, but you can integration test that bad tastes haven't happened.
I think Apple lost a bit of credibility after the round-corner fiasco that still persists on Tahoe.
They wrote the HIG before Alan came in and trashed the place.
Wasn’t it introduced on Tahoe? (Perhaps my memory is failing me here.) Do you mean it still persists on Golden Gate? They seem to have addressed the majority of issues I heard about - unless you mean the issue is that rounded corners exist at all.
See: https://medium.com/@makalin/reclaiming-the-screen-a-develope...