I have never heard of a restriction like this, (also when I was an APD at PDT I didn't have this limitation) ...... The only requirement is that they are employees of the air carrier. That being said I don't see PDT doing a type for FO's due to the FAA approved training curriculum for PDT still requires a minimum level of training that would need to be met so there is no real saving for the company. Plus giving a type makes you more marketable something I am sure your management does not want.