EX Ruffian is OTG?

The other day I was playing arcade mode on hard difficulty against a T.Hawk Cpu and was about to win the round by baiting his forward walk to EX Ruffian. However, when I finally saw the opportunity and executed the move the T.Hawk use his Ultra 2. The move connected and I evidently lost the round.

Could someone explain to me why this move registers as OTG when its clearly a grounded slide?

you’re airborn for a good portion of the move. this is also the reason why you can’t be grabbed out of it. in slowmo you actually see that he kind of jumps.
not only ex ruffian, lk and mk ruffian too. ex and mk are from the 2nd till 7th frame airborne, lk till the 10th.

Makes sense, thanks for the feedback.