How would this be any more accurate than astap (without distortion correction)? It seems that with or without distortion the platesolve would be able to determine precisely the RA/Dec coordinates of the center of the frame. Considering any detrimental impact from distortion would presumably be centered precisely around the center. (Yes, I'm using Roland's definition of distortion for this logic).
It would be interesting to hear Han's take on this aspect of ASTAP.
The center coordinates are determined based on the solving of angles and distances between stars. If these values are distorted then the center coordinates can be miscalculated to some degree. So, certainly the RA/Dec positions of stars will be wrong if distortion is not accounted for.