the caulk/whatever, when dealing with PVC must be of the expanding type and there must be an annulus to fill or it cannot squeeze the PVC as it melts.
If there is no filled gap and the caulk is merely sealing any minimal gap left, once the conduit melts, what happens? An open hole. If the caulk was merely on the surface of the rock, it would not have anything to push against so as to pinch the pipe. It would simply expand outward.
so, annulur gap is required. there are minimum and maximum gaps allowed
it must be filled with an expanding caulk or approved material.
and you thougth all us wire jockeys did was yank romex around the house