I mean how practical is it in matches. I don't see it being too useful. The smoke would be better off blocking DD or window. I don't see much use in it. It will take a while to settle, so it can hardly stop mid rushes I think.
Maybe you'd want to do it as CT if you wanted to move someone from mid towards A or B and the first smoke you put up at those doors to block potential picks is going down soon? Although Ts might see the direction it comes from, which is a huge negative.
You're probably right in that it's not very useful.