If you have a pre-approved plan that permits it, seems like it would be hard for them to argue that it isn't permissible. I wonder if some other provider might have decided not to allow it in their own pre-approved documents not due to legal reasons, but for administrative convenience. Sometimes they have some plain vanilla options only because they want only cookie cutter plans, or they don't want to deal with the 414(s) testing, or they don't want their clients to screw up because they (the clients) didn't test, etc., etc...