I always thought that "bio" was the same as corked just thrown over the front. Difference between bio and cork is the same difference between misty and rodeo, it's just the way it's thrown. Which makes me ask... How come no one throws bios anymore?
if you want to compare d-spin is to cork as bio to misty and rodeo to flat
d-pin, misty and rodeo your head goes under your feet during the spin
and in the cork, the bio and the flat your head never goes under