You don't get my point. No matter the result they will provide you in this five minutes they can reveal hash they chose by their own.

Example let's say epicdice makes all games being lost in this five minutes, they can calculate hash which will justify it and then publify it.

Other thing:
Why to even use transaction hash now?
It doesn't make any sense in current implementation, if there is server hash, you could just forget about transaction hash and just reveal server hash once per five minutes.
In my opinion they got lost in their ideas.