Heat pump ?

[Jalsup]

I have a 2023 Montana High Country 311RL. It has 2 Coleman Mach AC's, one in the living area (that is also a heat pump) and one in the bedroom. The 2 thermostats are AirExel models.. The bedroom thermostat only controls the AC in that room and has no heat mode. The living room thermostat has settings for AC in the living room, the gas furnace everywhere and the heat pump everywhere. The living room unit shares the ducts with the AC in the bedroom when the heat pump is on. Of course the AC in the bedroom must be off for the living room heat pump to send warm air to the bedroom. I was told that the heat pump is effective at an outside temp of 40 degrees and up. Below 40 you turn off the heat pump and turn on the gas furnace. Last night the temperature dipped to 39 and the gas furnace came on while we were sleeping. I know that most houses with a heat pump have a heating element that comes on that assists the heat pump to heat in colder weather. Is that what's happening here? Is the gas furnace coming on automatically to assist the heat pump like in a house? Should the heat pump stay on while the furnace is going or should it cut off? Can't find anything in the owners manual to address this and hoping someone has the same setup to advise me.