In cases of high grade notes, it could be something like a trim, not necessarily that it had been pressed. Either that, OR it could be that it was pressed lightly, as the original certification for Devil's Face variety has to contain some original rippling due to the printing process to obtain the Original Certification. I'm not sure on the higher denomination notes, but I think it goes across the boards. They used excessive ink, and thus caused rippling in the heavily inked areas. This could have been seen as a flaw to a collector prior to grading, and maybe they flattened it out a bit.