They seem to enforce and neglect that rule whenever they have felt like it. Even going as far back as 5th gen they bought in Niigaki who was in another audition and did work for Tomy appearing in commercials.
Honestly the whole idea of fresh faces only is just silly if they are talented and fit it shouldn't matter where they come from. Even if they were in say an indies idol group before and joined it wouldn't be a big deal.