I will go with "legitimate f-up" too. Elon Musk has been pretty vocal about Signal in the past, mostly positively. If blocking Signal URLs has been intentional, he would have probably have mentioned it somewhere.
Shortened URLs are dubious by default. It is also possible that there really is a lot of spam/scam happening on Signal right now with signal.me URLs as an entry point. I mean, why not? Every messaging platform can be used for that, even more so if end-to-end encrypted as it makes spam detection harder. In fact, one of the first messages I received on Signal was an obvious scam from a user pretending to be Amazon.
Shortened URLs are dubious by default. It is also possible that there really is a lot of spam/scam happening on Signal right now with signal.me URLs as an entry point. I mean, why not? Every messaging platform can be used for that, even more so if end-to-end encrypted as it makes spam detection harder. In fact, one of the first messages I received on Signal was an obvious scam from a user pretending to be Amazon.