Mirroring the sibling comment here, moxie has been very open that this is his project, top down. He moves as fast as he wants and he steers wherever he thinks is appropriate. This is one of the main reasons Signal doesn't federate - he thought it'd bring iteration speed to a halt.

(And let's be honest, if XMPP and the A3-sized spreadsheet you need for to pick a client based on XEP support is anything to go by, this is not undue concern.)