My understanding is that code requires 3 + ground even if the device does
not. Others here seem more qualified for a definitive answer on this.

That is simply not true. You only need to provide conductors to serve the load
plus a grounding path. If you have a neutral load on a 240v circuit, you need 4
wires or a raceway system that provides the grounding path and 3 wires.
Otherwise 3 are fine. The only issue is reidentifying the white wire to another
color in a 2 wire plus ground cable.
White green and grey are reserved, any other color is OK for the ungrounded
conductors.