Frank, it is probably worth taking Dick's word for it; he isn't known for undergrading routes! My memory of the route goes back quite a ways. I think Wunsch and I were both climbing 5.12 at the time and so the route, though really excellent, didn't seem hard. I think it is easier than, say, Transcon, but of course nowadays people get that wired and forget how hard it is onsight. I also don't have any idea whether Dick's grade might refer to the last pitch, which I've recommended avoiding.
As for protection, I really have no idea. Isn't the first steep crux on Grand Central also PG? If so, it could be that the PG comes from that part.
My memory of the protection on the Penn Station part is that it was tricky to protect the delicate step right at the top of the Grand Central starting dihedral because of a very shallow and maybe also flared horizontal placement, but after that the pro for the variation was closer to G than PG. If the tricky placement (and I don't know if it is tricky any more with modern gear) blows, there is still a good nut just below foot level, but there would also be a swing back into the corner, so that could account for a PG rating perhaps.
The delicate step right might be 5.9, no harder, unless you are tall enough (I think well over 6 feet) to keep your feet below the slab that forces the delicate move.