That is one thing I hate about the dealer doing the 10k, they have proven that they can't seal the covers well even from the factory so when the service is done those that had no problem may have them start leaking. These bikes need a better gasket for the valve covers.
The only way the dynco could have done that is they push the bike to redline and that is when pressure is the greatest in the crankcase. It may be that you don't ride the bike as hard as they did during the dyno. Since I ride mine like I'm mad at it that may be the reason mine leaks so much. The current leak I have will stay dry until I take a hard ride, but If I put around it stays dry.