Why should he give BTC back just because they know his address and a name?
When you look at their TOS, I don't see on what ground they demand the BTC back, as they say that "Orders, once executed, are final and irreversible." So, if orders are indeed irreversible once executed and if PDAX is just an exchange between the two users, how come they ask money back?
I agree with you on this. Another way to look at it is, what if the tables were turned, what if the user was the one making this demand. Would the PDAX team have complied? This goes above a normal compliant to support, should the transactions have gone on within there terms of service, then, it could be said to be the users lucky day and they should live with it.
Then again, we heard just one side of the story as he didn't share what exactly PDAX told him is the reason for wanting the BTC back so there might be more than he is telling us.
Anyway, strange behavior from an exchange and if it's true what that guy is saying, I would contact the lawyer and let him deal with them.
The reason was stated there by the PDAX team and it says overdraw, probably, there was a limiting withdrawal amount according to how i understand this and should it be that due to some technical issues, that limit was by passed, its not the users fault and besides, they have no right over his or her coin. They should just look out to tightening there loosed ends.