it varies, from cardroom to cardroom, I for example will bind the player to passive action if I deem that the best way to proceed, where they have accidentally exposed their hand, it can get really messy if someone accidentally exposes their hand, and then tries to freeroll the hand.
It's a judgement call at the end of the day, their is no right or wrong way to handle a prematurely exposed hand, the rules clearly state that they (the player) will not have a dead hand, but other than that it is up to TD's how to handle it.
Just another situation where a player leaves himself at the mercy of the floor!
Best
Stu