Our previous coach, 2010 Damon Astoria, had 1 heater and 2 A/C's. Just like yours, the heater and front A/C was controlled by the front thermostat and the rear thermostat just controlled the rear A/C even though it was marked to have a heater setting. When I asked about it the dealer indicated that was how they were supposed to operate. The heater can only be controlled from 1 thermostat, the manufacturer just used the same thermostat in both places. Now, if you have 2 heaters, then the rear would controll the rear heater and the front would controll the front heater. What it comes down to is that a single device can't be controlled from 2 different sources
Good luck,
Keith