Do they not have "internal" releases for these root components that are not depended on by everything, so you aren't having to wait 2 days and use a gazillion hours of computer for every single change though?
If you change a core lib CI will build and test relevant code, which will be a lot, but it will scale over a massive CI plant.
Still best to run unit tests locally first of course!
Are you speaking from experience or is this a guess?