[PurpleRamen]

That is only true if the outside contributes things that facebooks actually needs and if they are on a level of quality which facebooks wants. Often enough projects grow beyond the initial goal and at the end the maintainer is buried in meaningless work (for his own goals) and can't focus anymore on his own important things.

[imbiased]

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.