"Uncopyable" would not be buzzed for being synonymous, although I think it would be a puzzling clue for the contestant.
The category syntax was driven by a few factors: first, and foremost, if the category was already used in a previous Winner's Circle, they recycled the old card. Other factors would be the syntax of the adjacent boxes (avoiding a series of "things that," "things that," "things that") and the space constraint of the box.