The problem is really in Google Assistant. It supports Thermostats and it supports Humidifiers. But it doesn't support the humidity reading from Thermostats with humidifier control, so therefor you cannot get humidity readings from such a device, and HE doesn't support humidifiers in Google Assistant. So you cannot get humidity readings from HE to Google Assistant.
You don't need to install an app to get the temperature in Google Assistant/Home. Here's how to do it.
