I don't do my HST's this way but if I wanted to make a strip of them I would cut my strips at 5" if I wanted 4" finished size HST's. The rule for HST's is add 7/8 inch to the finished size and most people round it up to 1 inch and trim back down. I've looked at tutorials on the tube method and it still appears that you'd have to have 5" fabric strips to make 4" finished size HST's.
I'll be curious to see someone explain how they turn a 3" strip into a 4" square.