The girls should get to wear pants and longer shorts too if they prefer! The fact that both of the sets are genderlocked means they will never unlock them in the future. The only way to do that would be to change both sets so one displays unisex pants and the other unisex shorts, or they would need to add 2 entirely new sets so that 2 sets are with the pants and 2 with the shorts and all 4 everyone can wear. Which is a lot of extra work they'll never do.