I reported this same issue in the main Google Home thread. @mike.maxwell was asking for thermostat and driver details, so it may help to post those. Mine is a centralite Pearl with the Generic Zigbee thermostat driver.
I am tempted to create a virtual thermostat and test that but I don't think it'd make much difference since it doesn't appear HE hears from google about the request at all despite reporting success. I have tested this on the 2.x update and have the same results.
I'm using a GoControl GC-TBZ48L thermostat with the generic Zwave thermostat driver and it doesn't work for me either. When I go to the Hubitat device page for the thermostat I can change all its settings from there so it isn't like the driver isn't able to control the thermostat. Nothing shows up in my logs to indicate Google is communicating to the thermostat when I try to use Google to change the temperature.
I am also using the generic thermostat driver with a couple of Remotec ZTS-110 Z-wave thermostats with the same results. Can change mode just not temperatures with Google Home.
I haven't gotten there yet but I was planning on creating Virtual devices that would set the thermostat to a specific temperature. This would be my 1st shot at limiting the authority of voice command changing the temperature.