Not sure I have ever heard of anyone blatantly telling an internal applicant they had to do this. However, the ABIM research pathway is a little like this...you get a guaranteed spot in exchange for being a cardiology fellow longer. I think some cards programs would definitely be more likely to accept you if they thought you were future faculty material vs. likely to go in to private practice, but I don't know that they will overtly say this to you (or promise you a spot for saying you'll do it). I don't think they could write a fellowship contract so that it included 3 faculty years tacked on the end, either...but I could be wrong.
