I've seen few moments where we use thing string. Is that bad? It leaves you at an advantage and you can do F12>>Swamp Hands for a low mix-up, as well as F12>> chain throw menace, so F12 MB cleaver also must be considered.
I dont use it cause of the frame gap. You can say "well if I condition them to block cleaver (which most characters have to block) then I can do the next 2". But if you are already making them block, then you always go for the grab.