Ultimately it will depend on what devices are being used to determine presence. It is strongly recommended that the phones for ALL members of a household participate in presence sensing based on location. In addition it can be configured to use other supported devices like the thermostat itself to detect if someone is home.
Use some caution if using the Home/Away routines to do anything that is security minded. You may not want a stranger walking through the house to cause a change to Home mode.
https://support.google.com/googlenest/answer/9251759?hl=en
https://support.google.com/googlenest/answer/10000312?hl=en
