
Originally Posted by
Gray
Grabbing the waist allows you to take the back if things go sour, like how Rafa took Rader's back in ADCC. It looks like in the Cob match, he wasn't at the right angle to grab the waist because in other matches that seems to be his preferred.
notice that rafa is using this position to get to the back, not to finish or to get on top. grabbing the waist offers you a chance at the back, but you sacrifice some control. that control is what leads to the top position if things go sour. getting to the back is great, but its a lower % option than sweeping for top position.
rafa is accepting the loss of submission and trying to get the back there, thats a different philosophy than i am presenting.