Hypothetically speaking, if it was possible, is there a better punish in the game OoS? I can't think of any that kill at 80, have invincibility, and hit on frame 7.
Jump squat's 5 frames apparently so that's a 12 frame punish? Just for reference that could punish almost all of Ryu's moves on shield, except for light tilts and jab. Though honestly if someone taps your shield, unless it's a giant hit like Ganondorf's fsmash, odds are you'll only have the 7 frame minimum shield drop time, and Ryu can just drop shield jab (some sources say jab is frame 2, others higher, dunno which is correct) into true shoryuken punish in 9 frames.
I'm pretty close to going on a tangent of figuring out the best OoS options now.. I'm trying to remember but, I think if you're not in shield stun your shield drops in 11 frames, so shield drop jab would only be 13 frames. In case anyone doesn't know, most of the time actually hitting a shield makes it drop faster than if you didn't even touch it. Shield stun actually negates shield drop time in more cases than not.
One thing I haven't taken into consideration is actually shield stun. Can you shield drop buffer shoryuken when in shield stun? I feel like it'd take an indepth feel for other character's moves effects on shield stun to even time it correctly and not roll. But it seems possible.
edit: the more i think about it i don't see why you shouldn't just shield drop jab into shoryuken. you deal more damage and it's really super duper easy. unless someone can think of another reason not to. hell it's better than some character's shield grabs.