It is not excluded. But as an art teacher, Xavier should've realized it wasn't Mark. Proportions, measurements. Even Sophia noticed he was taller. Anyway, perfect timing.We don't know if Xavier was part of the set up and he could of bee used as well.
Aiden may of bribed the other model with extra money or even threatened him to change places so Aiden took his chance to grope Sophia after all it looks like Aiden treats the whole thing(the tasks)as a joke