A few years back we tried to get an answer to this question...in the end we applied for a C1/D and with the identical paperwork we both got to the embassy on the same day... I left with a 5 year C1/D, my colleague with a C1/D & B1/B2 for ten. How these things work ? I donīt know.
BTW, the call center you call is useless: had a romanian student taking my call and way more than 100 USD later he and his supervisor still could not answer the friggin question...
Btw, then NO ONE bothered to check the Visa we had when we picked up the aircraft from Cessna....