[user5994461]

If so, they would have a massive problem upgrading libraries like numpy because there are too many and too big breaking changes between releases.

[jumpingmice]

Inside Google's main repo there are different build targets for libraries with incompatible API changes that are too difficult to fix all at once, e.g. there might be numpy_1_8 and numpy_1_10 separately.

Python at Google muddled along for years without numpy at all so it's not like anyone would be seriously harmed by having an old release in the repo.