Thanks for the heads up on the new cutter, will get to running the new items through the cutter gauntlet shortly. Oof more things with S, but cutter named Hidden Reflection, so +HR will stand out and sounds like hair so that's somewhat useful to remembering what it does. We already have had multiple recolors of items from the TBT mini-ci so hopefully there'll be expanded access to this cutter across the next month.
My guess of why it couldn't be rolled into PruningShears is what layers it was originally designed to modify. For example [speculation] if Niwamori only had mod layers 1) infront of the avatar's face, 2) infront of the hair/head 3) behind the hair/head. And if Shattered doesn't have 1) infront of the face, but instead has 1) between the back of the head and hair, it would work for extensions better but be unable to modifiy facemods like PruningShears has a few times.
although it seems like it could also have been possible to modify/expand the PruningShears layers to cover the new ground, I don't know enough about the structural differences of the cutters to know if that was even feasible.