Yes, they are very careful about not breaking userspace. That has nothing to do with holding the _user_ in high regard, though.

The sweeping changes in Linux are amazing, but they also break a lot, frequently, and the testing approach leaves a lot to be desired. I am old and a former embedded coder, I understand how the 90s developers feel about unit testing, and I am sympathetic to the idea that test-driven-development and heavy UT in modern teams is often completely out of control, but Linux is distinctly lacking in real testing of independent units in isolation. I am aware of kunit, kselftest, etc.