Given the trajectory of Microsoft products it stands to reason Github’s future is uncertain. Also Git is ultimately a hosting platform that any competent software shop can recreate; the people behind the platform matter more than the platform itself.
As someone who is intimately familiar with GitHub’s data models, I wouldn’t say that replacing it is so technically trivial.
But even then, you are right that that the moat of social cachet and implicit trust is still more valuable than the moat of technical implementation.
True eventually, but not today