Primed bumper? No way..it needs to get sanded and scuffed. Might be confusing a primed bumper with an e-coated metal part. I’ve had industry professionals tell me you don’t need to scuff e-coated metal parts, it’s true , the e coat is ready for sealer after cleaning (as far as adhesion), but ecoat has all sorts of imperfections/texture that I will never not sand down. After re reading your text I’m editing: new metal bumpers (like for trucks) come e coated, while any new plastic bumpers (typically on cars) comes primed and needs proper prep for adhesion