Hm, actually it looks like he has IASA exactly one frame before AC. It's almost impossible to reproduce outside of SH fair on BF platform. Logically, a one-frame window means that early aerial options are impossible; this only applies to specials done while landing on this exact frame.Also if this doesnt apply to DK whats happening in that video? He even has that weird down b thing too.
This is weird, and doesn't seem very significant. I'm pretty sure it really is exactly 1 frame.