I think the issue is that if you put a sensor in a group and that sensor is on, the group state in unknown. This is a my alert group of groups. Each group has one sensor or switch which is automated to disappear when the switch / sensor is off. There are 36 groups in the alert group which reduced my previous front end by two pages. A possible feature request would be to add visibility to entities based on a state parameter (or hard coded to their own state so the parameter would be only on/off). You can see the unknown state of the groups with sensors in them below.
