No you are being dense. You are assuming he is not moving his ass because no one has told him or that he needs to be told. That is quite a stupid assumption IMO. I think he knows he needs to speed things up but just isnt doing it.
The question is whether he learns to or not but it is something he has fix as again it is obvious to everyone. He just needs to do it. Not everything is an issue of coaching. This is an issue of him needing to adjust to the speed of the game.
He is looking downfield longer than he needs and I am presuming after this many weeks that the HC is teaching him to look downfield before running!
Or the HC is failing to reach him on when to run vs. when to look to throw.
Either way, the 5th year HC is far more responsible for this than the rookie starting game 4.
When he plays free and loose, he has good instincts when to throw and when to run.
He has looked far more uncomfortable in Nagy's system more than he has ever looked confident so far.
He has SAID DIRECTLY that he got spooked to the point of "goosebumps" vs. CLE and I think today as well in some spots.
The fact you keep separating Nagy's role in his QB's play from Fields' role is bizarre and irrational.