Agreed Pete. Your argument that "the NEC is not privy to the internals of the unit" is exactly why I agreed with both Dennis' first response and your comment here that the manufacturer's specs supersede the NEC. Well put that ""the NEC is not privy to the internals of the unit." Makes perfect sense.
It's about a 90ft run in wire length. I realize I'm getting up there and voltage drop comes into play, but not enough for me to be concerned about increasing the conductor size from a #8 on a 32.5A load. If it were a 38A load, I'd run the VD and see if I need to increase the wire size, but I feel confident #8 will suffice.
Interesting stipulation though that distance of the run / voltage drop could force your hand in sizing the circuit larger than the manufacturer requires. I suppose that would be a case in which the NEC beats the manufacturer's specifications