Given that play was identical on the two bonuses, then either BOTH were "abused" or neither. They cannot claim only the reload was abused, and not the first.
Their lack of a reason shows that they are just guessing, no terms have been broken, and they are just sore losers, you did something "impossible", which was to beat a sucker's game twice on the trot, therefore you simply HAVE to be "cheating" in some manner, but they have no idea how, but know that without the bonus you would probably not ended up ahead.
The typical "bonus abuser" will take the juicy first bonus and run with the money, they would NOT return again for a lesser offer, this is what "loyal players" do - giving the casino a chance to win back some of the money.
The ID has nothing to do with bonuses, it is becoming routine whenever a payment is made to a player.
The
PAB process may reveal what is going on, but on the face of it, this just looks like a rogue casino miffed that a player won on a high house edge game, one that would normally be a "cash cow" for the casino.
I have heard worse though, a player of SLOTS was accused of "abusive play", and this surely has to be impossible.