I dislike the Tier 1 rule "All core developers are responsible to keep
these platforms, and thus
In my experience, "Everyone is reponsible" means in practice "nobody is responsible". IMO you must also put two names in front of each platform. Otherwise, nobody will fix them when it will be broken, and the best that we will be able to do is to just revert the change breaking the CI which prevents adding new features just because nobody wants to fix the CI.
Sometimes, a broken CI is unrelated to a Python change. Things break, *all the time*, for many various reasons including vacuum cleaners (*)!