Paper Tiger is a cool name for a terrible product; They should require a license to operate one (along with a Silicone Applicator’s License).
Any paper that ‘resists’ water, I dry peel the top layer off so the DIF or water can reach the wallpaper paste. If the paper face is stubborn, or too time consuming to remove, then a rough sandpaper (60-80 grit) will score the face, making the paper absorbent without damaging the drywall.
If I can’t spray, DIF gel can be rolled with a 9” roller. Same concept: keep it wet until the paper falls off the wall in large sheets without scraping. One wall at a time. Do not let it dry.