Being over the salary cap is not the owner's fault. He obviously had an AD card of 80M or below. Due to the lack of 75¢ players at some positions like OF he can miss on some players and be given higher priced players (the lowest available salary at that position).
It is to the owner's DISADVANTAGE to be over the cap in a mystery card league since he can't make one transaction without first complying with the salary cap. How often can you go through a mystery card season happy with every single player card you end up with? I'd say not very many.
Don't worry about him being over the cap right now. It is to his disadvantage, not yours.