you can OH ryu whiles he's in the air during his 6kp, it's hilarious
but yeah for some reason, in DOA5 and 6 (as far im aware) there are 2 airborne states, one that's partially low invincible so you can still get hit with lows and throws while airborne (Status: Jump) and one that's fully low invincible that can't get hit with lows or throws at all(Status: Jump Evade lows). it's weird but that's how they do it