Thanks for reaching out and we're sorry for the delay.
Here's a couple of questions to get a better view of what's happening:
Did you use your own phone to set up your Nest Thermostat from the Google Home app?
How many mobile phones are connected to your WiFi?
You can turn off Presence Sensing from the other device and observe your own phone if it is still going to have the same message.
Let me know how it goes.