Last year or the year before I got a hold of a load of pre build (already finished) frames from brushy with plastic foundation. Curios about the hole in the frame, I checked this morning and they do have hole drilled in them even with plastic foundation in them. But it really makes sense to me that you don't need the holes with plastic foundation, so who would miss them or want them. Until you use the solid bottoms for something other than plastic foundation.
I bought a pallet of preassembled frames from mannlake-there where no holes in them-this is something new to me as the frames i bought couple years ago had the holes--RDY-B