It's hard to tell but just for a jiffy on landing after the DFS Bite Corrin's helmet disappears (it reappares again right away for her F-Smash so really hard to see when for me without frame-by-frame). You can see it in the video if you put the speed to .25 (but would be easier with frame by frame). I remember that earlier in the thread there was a theory that Dragon moves cooldown eended when the mask disappears and this seems to agree with that.
IF that's the case, then the helmet disappearing on the ground means either the DFS bite (charged that long) cooldown last the amount of time corrin takes to fall from a full hop or it takes longer and autocancels (but the animation looked like it was ending anyway so it's probably the former)
I still cant really tell without frame-by-frame but male-Corrin's helmet disappears right above or as he lands from the Nair. Later in that sequence though (not in the GIF) he does a SH Nair and the helmet disappeared when he hit the ground so maye it autocancels? He didn't really act on landing though.
On the other hand, the SH Bair he does in that video sequence kept the helmet for a while so it probably doesn't (plus it just doesn't look like it).
That all depends if the mask theory is true though and I doubt it since in the sequence at around 31:36 Corin does a DL jump into Dair and his helmet disappears right at landing and I really don't see that move being quick to act out of.
Here's a video link for convenience because I don't have access to GIFing atm
(Just a random observation, it's strange that the first hit of jab doesn't have the mask since it uses Dragon Fang?)