it just can, ive heard numerous cars, fwd, rwd, its just the way it loses control when hydroplaning.

im guessing whatever tire reconnects traction with the ground causes the vehicle to aim biased to what wheel starts pushing again (i.e. if whole car starts hydroplaning [and sometimes you dont know til its too late] and say the right rear gains traction, the rest of the car is still kinda 'floating' on the thin layer of water and its as if the car was being driven on ice using only the one corner of the vehicle).

i could be wrong, it might also have to do with people overcorrecting in a slight skid and etc i just rmember hydroplaning is when its riding on a layer of water and means you are not in control of the cars movement for those brief periods of time. i dont know if the aforementioned paragraph is true or not though thats just my semi-educated guess. i remember that if you can turn the steering wheel and your car doesnt turn, you're hydroplaning (or you got some sloppy loose broke ass steering)