Dont see how they could. The servers are real apple devices. Apple has no way to know if this is a mac from a real user or somebody proposing a message bridging service to non apple users. Dont see why they’d care either as they make money from the purchased server infrastructure.

This has been around for a few years now as Blhebubble, and they haven’t blocked it.

There’s a couple other bridge services out there too, and those haven’t been blocked… Yet.