How is it relevant to anything whether or not he has other clients?
Totally 110% irrelevant.
On the other hand, didn't PDJT say he didn't even know about, and therefore didn't approve, the payment to Peggy a/k/a Stormy a/k/a Stephanie?
If PDJT indeed made such a statement and if it was truthful, then it would seem that maybe Cohen was not actually representing his client, but rather was acting sua sponte in toto -- in which case an attorney-client privilege could not exist.