How do you prevent data exfiltration? I mean, in theory you could restrict the visibility of repos to the user based on team membership/roles and so prevent a single person from unauditably exfiltrating the whole Windows source code tree. In contrast with a monorepo there likely won't be any alerts triggered if someone does do a full git clone, except for someone saturating his switch port...
What would someone do with the source code for Windows? No one in open source would want to touch it. No large company would want to touch it. Grey/black hats are probably happier with their decompilers. Surely it would be easier to pirate than build (assuming their build system scales with most build systems I've observed in the wild). No small company would want to touch it.
Anyway MS share source with various third parties (governments at least and I believe large customs in general) so any of these are a potential leak source.
