I don't know what it is, but I can't stop myself from jumping off once I see them trying to recover. I usually SH off the ledge and attempt a Dair above them, but it's tough to make hit, IMO, though you wouldn't know it from watchng that video your talkin' about. He seemed to make it hit em' while they were floating around IN FRONT of Oli, whereas I an only do it about 50% of the time and only from directly above them. Maybe I'm too obvious with my movements or somethin? I'll have t take a closer look at where the pikmin actually makes contact... Sometimes jut runnin' off a Fair'n em is just as effective, ya know? Just not as fun. I love that huge risk an Oli player takes jumping far off the ledge to make it over and spike someone down.
I've spiked before as low as 30-40% against really dumb opponents,thanks to a red or purple pik. If I miss, momentum usually pulls me down to nearly off screen below the stage, at which point the chain is useless; not too far from the ledge just.. occupado. -_-;
I summary, yes, I usually attempt a spike, especially after 50% or so. I really need to work on my technique though... =\