I'm not so sure; the problem is that you have to release the stick extremely quickly after performing the shield drop, which is difficult because of how precise and gentle you have to be when you're performing the shield drop. I have only recently even attempted to do this (since it's only now that I've become consistent with both shield dropping and platform drop cancel nairs), so maybe I'm missing something or making it out to seem harder than it is. I've never seen it done in a game (actually I've never seen it done in a TAS or a teckskill demo either). Are you able to do it or do you know of anyone who is (and if so, could you explain if there is some kind of trick to performing it)?
yea i mean, i guess it's harder than i gave it credit for; just, i happen to have done it a couple times in matches in the past few months just by like...trying to, in singular situations. so it didn't seem too crazy. but just now i got about 1/5 vs a stationary character. i'd imagine someone out there can do it much better than that, but looking at frame data, there might be some other factors that get in the way.
so the techskill aspect of it is getting the shield drop, letting go of the control stick immediately, and pressing A within the window. the thing is, you only have two airborne (animation state "Pass") frames to input the nair (just like with a regular drop) and have it drop cancel on hit. however
unlike a regular drop, you will be airborne the frame after you hit the shielddrop control stick input, so the stick has to get all the way back to Neutral in <2 frames in order for you to be able to nair in that window—with a regular drop, you have <4 frames for the control stick to return to Neutral, since you can input Down for two frames and then let go, leaving <2 frames of animation state "Squat" and <2 frames of Pass for the control stick to bounce back.
the problem is that that means it's probably super controller-dependent, since the major execution difference is reliant on how fast the stick can bounce back to neutral on its own, rather than anything about your personal execution... like even if you can shielddrop really well, and you're super fast and only hit the shielddrop input for <1 frame, you still need the controller itself to also be fast enough.
so i guess from a theoretical standpoint, if there's a "trick" to it, reducing the travel distance for the stick would help out. meaning, shield dropping straight down rather than towards a corner in the control stick gate probably helps—which
is actually how i do shielddrop nairs and fastfalled stuff.