Yep I played with Zac for a couple of days, he told me you talk a lot of languages.
My italian training is showing up results, Zac is doing great lately
Actually it depends, I can always pivot a retreating Nair/Fair to be safer.
The point is, if I'm too close to my opponent and he thinks I might dash back to adjust my spacing, he's going to overshoot, and I'm going to be punished 'cause I'm probably too close to dash back and Nair in time, so the better solution there would be doing something in place.
But let's assume the Marth is trying to bait an approach by DDing, if he's doing it right, he won't be too close to be punished easily, so he'll manage to have enough room to react to an overshot run/aerial with backdash>pivot grab/Nair.
Even in the case you misspace yourself you can always ASDI the aerial and grab, that's mostly what M2K does against Fox.
What you're saying is true, I'm just saying it depends heavily on the spacing of the players and how well they can read each other.