Whatever rate I get at the pool is roughly 97-98% or so what I have displayed as my total speed. So I am pretty sure this is some bug and he is not overcharging, since it would be very easy to prove.
I re did some checks and compared the diffs (without setting any static diffs nor redirecting anything, just with the logfile from the console) and things seem to match up.
It did mine 22 shares at 242h diff during the 90 seconds it's mining for the dev and the following 90 seconds 11 shares at 636H were mined for myself.
I guess I was wrong, still worth it for someone to investigate deeper.
Sorry for the false alarm.
For Optiminer there were "hidden fees" because he forgot to mention in initial releases his 15% fee. The fact that his miner was also "hiding" that fee, giving the users the impression of always having their full hashrate however 15% is mining in the background to another pool. This is what raised suspicions and got us looking into Claymore's fee to see if they really are what they claim to be.