This wasn't an oversight, but an intentional thing done by Sakurai and his team, as Yoshi can't do it in any official game except 3DS/WiiU. We're considering letting him jump out of shield.
He can jump out of shield in 64.
Eeyup... Brought his Falco down to 1 stock and around 70% using only Usmashes. From what I remember, he was both impressed and pissed.
Because Falco is a fastfaller, the move combo'd into itself 3 or 4 times doing 60-80% the first time I'd get hit, then two or three more would seal the deal, so if I messed up like 15 times across 4 stocks, GG. The other issue was that it was safe on block, so even if I knew it was coming, I couldn't reliably punish it except with lasers or trying to time an attack against it [kinda risky].
I'm impressed the move is that useful on its own, but when you factor in that he has eggs, fair, Yoshi foot, egg roll, and every other move in his arsenal, it's kind of obnoxious lol.