When I worked at Apple, they were extremely strict about contributions to FOSS stuff, even on your own time, even for simple stuff like bugfixes or opening a Github issue.

I am sure they have their reasons even if I don't agree with them, but it's made me very cautious about making PRs and the like while working at BigCos and making outside contributions to FOSS stuff.

This even more so, though, because of course I was doing it on company time, so I wouldn't really blame them for wanting to audit stuff to ensure I'm not divulging company secrets and the like.