I'm not up to speed on the technicalities but I've read AFM causes GM engines to burn oil. So yeah, changing the oil often may prevent issues, but I'd rather circumvent/delete AFM and have a truck that doesn't burn (as much) oil in the first place.
That Range AFM disabler works on any OBDII GM vehicle, so I'm sure it'll work on your wife's ride. It's what all the truck bros use and it leaves no trace once unplugged. Once I get out of warranty in a couple years I'm going to delete all that garbage with a cam and other toys.
On-topic, like others have said, dealerships are having trouble keeping a solid inventory with covid because new cars/trucks aren't being built as quickly. Demand is high and supply is low so I imagine getting any kind of discount do be challenging.