Just realized how stupid my question was. Thanks for the answer!

To cite the answer: "The normal force acting on the incline by the block does do work, but the normal force acting on the block by the incline does negative work, and the total work done by all normal forces in the system is zero... Therefore, the normal force can be considered a "constraint force", i.e. a force that does no work and is neither conservative nor non-conservative."

The answer indicates that the work the normal forces cancel each other out.