A company as rich as Apple should be able to QA their full supported product range without compromise.
They should be able to. It would be easy. But it is faster and cheaper not to, and companies are not single omniscient monoliths. Each department has their own targets, quotas, and deadlines, and while I doubt anyone at the top of Apple said anything along the lines of "ignore these devices", the ball was dropped somewhere in the chain of command, and the fact that nobody picked it up (along with experiences with past Apple updates) suggests to me that QA is much lower priority at Apple than some other places.
Testing and doc quality seem deprioritizedfor macOS. This is not good.