Ever since 1.1.0 hit with it still in, I've been pretty positive SSHC is intended. In the past, both Mega Man and Diddy had specials that negated minor hitstun, too, and those were removed pretty quickly. Shadow Sneak definitely can still work properly if they removed it. All they would have to do is prevent the shadow from being able to come out when Greninja is in minor hitstun, and that's far from impossible given that they already took away the shadow's ability to come out during a different state (landing lag). As mentioned, the move itself has received many, many changes throughout the game's lifespan, so it's not as though they've ignored the move. Much more obscure stuff has been taken away such as running Shadow Sneak, indefinite Shadow Sneak, and a method we used to have where we could activate the shadow while having our shield up and not having the shield auto-drop immediately, and yet, SSHC remains. Really, the only argument I can see for it not being intended would be the lack of any in-game hints pointing out this property for the move, but I feel that, with just how much they've touched the move and kept that in, that property is something the developers want the move to have.
As to whether it's dumb or not, Greninja has blindspots right in front of him for two smashes, a hurtbox above his head, and a counter that he can be attacked out of before the hitbox comes out. He's always been an... odd character, whether you're playing as or against him.