That's true. However, it doesn't really negate my point, it complements it. In this case, Apple could have a "test" that is: install the new OS under test on a

That's true. However, it doesn't really negate my point, it complements it. In this case, Apple could have a "test" that is: install the new OS under test on a machine, and see if performance degrades on other machines on the same network. You could have 10 people test it with 10 different networks. It's expensive, but Apple could heat their HQ by burning cash if they wanted. Admittedly, some things will still get through due to tests that you would only think to do in hindsight. But once you have the test, they won't get through again.