It is very difficult to compare self-reported temperatures! Really if you get into it, there are many crappy sensors, crappy thermostats, thermostats mounted near single pane glass, etc... I spend some time complaining about my Nest V3, many people did, but it's just too difficult to get a reliable measurement. Btw, in the end my conclusion was that the Nest was doing quite well. Just the Shelly and the Hue sensors were easily 1-2 degrees off.

Btw, what's up with Nest? I want another V3 in my new house, but they are not available anymore??