@MichelDiz, although this is slightly out of the scope of the question here, after reconsidering your point, I think the current behaviour is right according to GQL specs since this is technically not an error.
GraphQL
If no errors were encountered during the requested operation, theerrorsentry should not be present in the result.
The user can query on numUids (the number of affected UIDs) and check if the operation actually performed an update.