Good point. Although an OSS maintainer can be strict and refuse contribs on features they don't want to support. And by breaking down Nuclide, some individual packages like the Python debugger etc, probably can be very well defined and have a significant overlap between what they (Facebook) and other companies want, without much room for deviation. As opposed to say the general VCS support (they mostly want Mercurial that Facebook uses internally, whereas most outside users use git).

It still needs your requisite that contribs are of high quality.