Have you ever worked for a company that produced and sold anything? Do you really think that any company releases products only after they hit a point of perfection? Imagine all the scenarios that are already tested for software to be released, but I would bet there are millions of points Apple, and any other company out there, just can’t be expected to test and resolve issues on, prior to releasing software or hardware. As a company, you have to get to a certain point where you’re providing a good UX for the majority of users, and then as issues come to light, either fringe problems or widespread, address them in updates.
In regards to FaceID with Watch unlock, I can’t say that I’ve followed any threads about it not working, mainly because I (and my wife) have had zero issues. I get that I’m a single data point with this, but it’s also not something I’m seeing articles pop up about huge failures happening with it, so I’m guessing that just as I noted above, there are likely scenarios where it isn’t working, or isn’t working smoothly, or isn’t working all the time.
I’ve had Mail issues with iPadOS on my M1 iPad Pro going back a few iPadOS releases, started a thread about it and only have a handful of people experiencing the same thing, with Apple not even knowing how to resolve the issue, so far, so I am one of those people on the fringe experiencing an issue that doesn’t effect the majority of people, but in your scenario of Apple needing to wait to release software until it’s perfect, it would mean that everyone would be waiting for an update because Apple hasn’t fixed a problem that effects a very specific and small number of users. Again, you can swap out Apple’s name and use Google or Microsoft, or any software producer and get exactly the same experience.