If you book a room that is part of a reserved block for a convention, it is not surprising that the organizers have discretion to kick out unregistered people in order to have room for legitimate attendees.
Flock, as the event organizers, had every right to revoke his registration, because he was not qualified, and what's truly remarkable is the volume of respondents who are shocked and outraged that Flock was granted control of the hotel rooms in a block which were dedicated and promised to their conference attendees. For crying out loud.
Reading their email it seems like it was indeed under the event block. But the "called on my behalf" is a bit sus anyways.