This may help clear things up but keep in mind, my experience was with a 2007 33.5 TropiCal as well and it may be different from the OP's.
My coach had two A/C units, both DuoTherm. According to the thermostat, the front zone could cool and circulate with just the fan but the heating option went to "furnace" on the read out. In zone 2, the rear unit, it could cool, use fan only, and the heating option was "heat pump." There was no "Furnace" selection on the thermostat read out.
My guess is that if your A/C has a heat strip, that term would appear in the thermostat, but "heat pump" would not. Both A/C units are DuoTherm because they both will heat and cool, though the heating is done through different methods--heat pump, heat strip, or in sync with a furnace.
To the OP, does your coach have two furnaces? I suspect it doesn't, but can't be sure. What does the thermostat read out indicate when you want to heat the rear zone of the coach? If it says anything other than "furnace," then that unit zone will not heat the basement area. If it says "furnace" and you don't have two furnaces, the rear unit zone will also turn on the furnace, the same one controlled by the front unit, which will heat the basement. However, I've not seen any set up where a single furnace is controlled by both zone selections (doesn't mean that set up doesn't exist though.)
Larry, Eileen, and Finley
2004 Alpine 36FDDS
Third motor home, first Alpine, no need for another.