Not necessarily correct, HTC test the update after the carrier puts its customisations in for the simple reason that if bad software is released it reflects badly on HTC.
HTC could come back and say they are yet to test the software which would point to a 2 week waiting que (typically 1 week from start of testing) or if they have finished testing the software it could be any day.
Also it's not through IMEI, its through Serial Numbers and CID.
I suppose that's also true.
Been led round in a viscous circle with previous HTC phones and updates. It's either contact HTC which tell you to contact your provider, which then send you backwards.
Half the time I wonder who actually knows the real answer instead of directing it elsewhere.