Ah, yes. Thanks for reminding me. That was changed at some point and the server started to store separate relationships, see Inconsistent presentation (storage?) of artist-memberof-group relations - #2 by chaban
But that means that the existing plugin to split combined relationships into separate tags has become mostly useless. And I think we should have an option in Picard to actually combine multiple performer relationships for the same person into one. I added a ticket for this: