I suppose that there are times when it’s useful to have a ‘peer’ relationship (i.e. not directional) allowing for entities of the same type can be put in a group together. In this case, only one field is needed.
But I think the next question might be, “What is the meaning of the grouping?” and if it is because different groups of entities have different characteristics, then perhaps this ought to be solved using either:
- single- or multi-select fields (a.k.a ‘tags’)
- many-to-one or many-to-many relationship to another type (i.e. the ‘peer group’ type)
and then creating views to show entities grouped according to tags/groups
For the last option, the many-to-many relationship would actually show as a collection in the entity view and it would be possible to see all peers (by enabling the display of the corresponding field for the peer group collection).
For the other options, we might need to wait until this has been implemented to directly see peers in the entity view.