Even projects with a “stable” set of targets have too much churn for this to be practical. Just because you support “latest macOS” doesn’t mean my build should fail if I’m on a beta build ahead.
Please let me know so I can fix issues. Or let the compiler vendor know, sometimes they add something new to get feedback on how useful it is in the real world.
Yes, I typically run toolchains that are slightly ahead or different than the one that is actually used in CI. I don't think it is reasonable to think that projects will be using it, though they often do appreciate me testing it early for them.