If you think that Mastadon is in any way a 'competitor' to FB or anyone at FB gives a shit about Mastadon I think that the bridge you are trying to sell only exists in your mind. Programmers are lazy and almost always breaking shit; the probability that this is anything more than some sloppy code somewhere pruning an offending URL in a way that blocks more than it should is so remote as to be laughable.
Amazon will delete a review if it mentions alternative-to-amazon ways to acquire the product. It's a known tactic among our cybernetic overlords.
Because they feel threatened by your neighbor's garage sale? Of course not.
I imagine it's like squashing the ants in your kitchen. We aren't really afraid that one of them is gonna make off with the milk jug. But all the same we don't like them touching our stuff. So we implement that policy. Almost unconsciously.