When is the last time we asked them about that? If it’s been a few years maybe it would be good to check again. After all , the desire for “complete freedom to change the APIs” is usually a sign of a young library (or perhaps one with a lot of current activity). BoringSSL may have settled down.
OTOH, if they consider themselves primarily an internal Google library, where indeed they have the freedom to change all code that uses it (because monorepo), why are they even open source? What do they expect their open source users to do? Fork it?