Let's be honest here.
The only true block strings that Shulk can do from an aerial requires MALLC (as shown in this video), which is super situational, especially so if your opponent knows what MALLC is to begin with. In addition, in order to actually induce enough shield damage to do a shield break, in most cases the Monado needs to be in buster mode, which unfortunately not only makes MALLC harder but also much easier for the opponent to see coming. Otherwise, Bair (or any other aerial for that matter) is not safe on shield even with the added shield stun (sans characters that have high traction like Luigi, which is unrelated to the shield stun buff) without MALLC, making this shield break combo extremely unlikely and sub-optimal. This game has almost been out for a year and I still have yet to see people even getting close to using MALLC as a viable strategy to begin with.
And even if this was somehow a slight buff to Shulk, it doesn't change the fact that other characters will benefit from this change much more than he will, meaning that, relatively speaking, Shulk will actually be nerfed, especially considering that Shulk has pretty ****ty defensive options out of shield already.
Until I actually see an in-game example of someone using the added shield-stun to benefit Shulk, I have doubts that this shield stun mechanic actually helps him in the long run.