I think that's what the RAAPs were meant to resolve.
RAAP-1 Concerning Types Training makes interesting reading, I'm a little more confused having read it.
Here's what the FAA define an aircraft type as:
Type:
As used with respect to the certification, ratings, privileges, and limitations of airmen, means a specific make and basic model of aircraft, including modifications thereto that do not change its handling or flight characteristics. Examples include: DC–7, 1049, and F–27.