@Nizzore, I have the same situation. My 2017 model X and 2018 model 3 sit right next to each other in the garage. The model 3 will be near the garage ambient temperature while the model X always reports a much higher temperature in the app.
Years ago I included this on my list of concerns at a service appointment. They said all was fine. What I did learn from that was that there are a lot of temperature sensors in the car, and the model X seems to pull from a warmer location. Also, when I turn on the heat in the winter the app will show that the car is quite toasty when it isn’t at all for the passengers.