It’s supposed to warn of a flat - low pressure. However, the pressure is obviously not that low.
Note, the highway drive also involves a lack of braking. Brakes heat up the wheels tremendously.
So I think the computer remembers the “normal” status of the prior time I had the car on and gets confused.
I check pressure regularly manually because I note significantly better mileage on my typically crappy mileage vehicle. Extra 20-30 miles a tank on long trips.
In fact, to accomplish that, I have to let air out of the tires on long trips, especially when travelling significant soutward in the winter.
So, even when the tires are actually heating up (pressure increasing), the light is coming on. It only stays on about 10-15 minutes.
Only one tire or random?
Plus many of the control algorithms expect the sensor to be in valid range. Maybe try a run that would normally trigger it but at 4 psi lower.
Nitrogen is your friend. Check it out. Most tire shops maintain pressure for free when required, one-time cost.