If you've signed a contract that states working hours are between 9-5, I think it's not his job to communicate any diverging preference, that would be the job of management. If 50 hour work weeks are expected, put it in the damn contract.
We're both speculating a bit; neither of us knows what the contract said or how the conversation went during the courtship process. But regardless of whose fault the miscommunication is when it happens, both sides would be better off if they discovered the mismatch in values sooner rather than later, right? FWIW when I'm talking to potential employers I always have an open discussion around work-life balance expectations long before there are contracts on the table. It's a practice that has served me well.
True enough - we don't know the details, and your advice is sound.