I kinda get what you are saying, but… for me improv is a skill that is hard to train or to master and relies a lot on luck. Will I think of something cool now and then ? Will I get ideas ? How will my brain interact with this exploration ? Its hard to say that improvisation isnt highly reliable on what you get at that moment between neurones.

How many times have I thought of better, cooler or more adapted ways to do what I had to improv days or weeks later ? Time is a finite resource, and when improvising time is your enemy. The longer or shorter you have to think, the better or worse it might end up with.