Had the Low pressure warning on FL tire for the first time last week. Reset/Calibrated the TPMS through the menu (without changing tire pressure) and the warning disappeared.
As mentioned in the owners' manual and described in details in
this document, pages 104-110, to avoid a situation where a hot tire that is underinflated might appear to be fine, because the contained air pressure is at or above its cold inflation pressure, some sort of temperature compensation is done by the system.
Here is a wild guess: I assume this compensation is based on a hardcoded table/algorithm valid for tires filled with air. When tire is filled with nitrogen, the compensation becomes less accurate, hence the false warnings.
The TMPS behaviour that you have experienced is explained on p.110 of the above document:
System E had a different approach. When the user sets the tire pressures and initializes the system,
the pressure is referenced to the current tire air temperature, which is equal to the current ambient
temperature as well. If the system senses the tire temperature being more than 36°F (20°C) below
the initialization temperature for more than two weeks, the system sets off a warning and must be
reinitialized. The user is advised to recheck tire pressures (cold) and must reset the system at the new
temperature.