maybe you can assign certain jutsus to a few or jst one hand seal, like how naruto only uses 1 hand seal to do shadow rep. now, wheras weve seen him use loads before. so obviously can assign the jutsus you need quickest or use most often to 1 hand seal.

this would be why gaara used loadsa of hand seals in 66-67, because he had no need to hurry so didnt bother assigning that jutsu to a shorter hand seal sequence. the same with zabuza, except i think that he may not have used the water dragon very often.

jst a theory kinda makes sense in my head.