"Greetings Thomas
flying little Bugsmackers
but also renembering that a specific aircraft has specific handling characteristics."
Makes me think of another possible contributing factor that had me amazed when the FedEx got approval to allow their pilots to fly both the MD-10 and The MD-11.
The only similarity between the two besides the cockpit layout are the FCC's and LSAS in reference to operation. Otherwise they are a DC-10 and a MD-11 in their performance specs and general handeling.
Granted pilots bid routes and are likely to generally operate one type of airframe for the duration of their bid. None the less, going from an MD-10 to an MD-11 and possibly back has to be very demanding of their skillset and a negative factor in maintaining proficiency.