The way I've always seen the cursed seals is like this: because they're derived off of Oro's own power, unleashing them would be like inviting Oro into your body. As such, if anything, "lvl three cursed seal" would refer to the point when Oro actually possesses your body.

But hey, I really can't say how far Kishi's going to take this "power up" business... But I'll be hella pissed if he does take further steps into DBZ territory.