I would think the foam-core stuff is DWV pipe. No big pressure worries there.
It is. Sch 40 only refers to the dimensions. The DWV pipe isn't meant to withstand as much pressure, but I believe the concerns raised by the OP were related to the collapse of the hole. Regardless of the pressure the pipe is rated to contain, a solid PVC pipe will withstand more crushing pressure from above than a foam core one.