It's a pretty low bar for any dog that doesn't have major behavioral issues; I'd expect any dog with a non-dumbass owner and a good home from birth to be able to pass. Even many hard-core rescues could probably pass after a few years in a stable home.
A variant of this test for airline travel would probably not be too hard to design.
One of the problems with making any particular test mandatory is that the test operator can price gouge and then genuine service dogs will become even more expensive. So, such a rule would have to be paired with price controls on the test.
