I'll grant that the conspiracy theory does explain the facts you mention (as well as the fact that Signal shares contacts with OWS), but I think that a simpler theory explains the facts too: the the OWS guys really do want to get some crypto into the hands of the masses, and are willing for their product to be less secure than it could be if it means that end users are more secure than they'd otherwise be (i.e., they believe the alternative to Signal-as-it-is is not Signal-as-it-could-be but rather SMS).
Tying things to a phone number makes sense in order to reduce Sybil attacks, but I think that OWS could operate a phone-number-based identity service which would be relied upon by federated Signal servers, reducing the degree centralisation while still preserving Sybil resistance. This matters because without Sybil resistance it'd be pretty easy for a malicious party to send a Signal user 10,000,000 messages per second, saturating his data connexion and depleting his battery; tying identity to phone number makes it easier to limit & block such bad actors.
Tying things to a phone number makes sense in order to reduce Sybil attacks, but I think that OWS could operate a phone-number-based identity service which would be relied upon by federated Signal servers, reducing the degree centralisation while still preserving Sybil resistance. This matters because without Sybil resistance it'd be pretty easy for a malicious party to send a Signal user 10,000,000 messages per second, saturating his data connexion and depleting his battery; tying identity to phone number makes it easier to limit & block such bad actors.