The “Device Info” page lists any Automations, Scenes, and/or Scripts where a device is referenced. This is useful information to have readily available while working with a device and helps to prevent these references from being overlooked.
Equally useful, but currently missing from “Device Info”, is the list of Groups a device is a member of. I propose adding Groups to the “Device Info” page in a manner similar to Automations, Scenes, and Scripts.
It is generally not recommended to use devices in groups, automations, scripts and so on.
The use of entities is the best practice.
You are correct. In fact you can ONLY group enties.
That said, if you add an entity to an automation or script, then you see this on the “Device Info” page of the associated device. However, if you put the entity into a group and then use that group in an automation or script, then there is no reference. It just kind of gets lost.