Yeah, the Copyright Clause is pretty unusual. More than literally anything else in the Constitution, copyrights and patents actually are supposed to be judged in light of what's better for society.
Most stuff in the Constitution gives the government the power to do X (sometimes stating explicitly that it's for reason Y). The structure of the copyright clause is that Congress has the power to do Y, using mechanism X — a strict reading of that means that the government cannot do X for reasons other than Y, and cannot pursue Y using means other than X, and definitely shouldn't do X for reasons of not-Y.
Most stuff in the Constitution gives the government the power to do X (sometimes stating explicitly that it's for reason Y). The structure of the copyright clause is that Congress has the power to do Y, using mechanism X — a strict reading of that means that the government cannot do X for reasons other than Y, and cannot pursue Y using means other than X, and definitely shouldn't do X for reasons of not-Y.