A nice thing to do for sure but whether it was done all off his own back I'm not so sure. He's a celebrity and celebrities are always on the prowl for good PR oppertunites make no mistake about it.
We all know the kinda guy he is already, not exactly a nice guy I'm afraid, typical mega billionaire movie star. Its not his fault I must add, this is how most movie stars turn out...PR hunting narcissistic money grabbers.
Whose to say what went on behind closed doors, who's decision it was, whether WB had anything to do with it, if money is involved, film promotion etc...I highly doubt it was all for smiles.
End of the day he did a nice thing yes, but don't believe everything you see or read (surely you all must know that).