Owning subgraph for a field in Explorer

[cosmincatalin]

What determines the owning subgraph (service) that is displayed next to a field in the Explorer?

I am in federated scenario and can see that for example the id field for a type is listed as belonging to a subgraph, other than the master owner. It is also true that the said subgraph is extending the type, but should probably not be listed as owner 🤔