I think the topic says it all. This is a mistake which should be corrected. For example, with
https://musicbrainz.org/release/df990224-bc9e-49df-a58f-2cd503fb26d4
Jaikoz adds “Sarah Kwak” as a second conductor. Clearly there can/should ever be only one conductor at a time! And the role of “Leader of the Orchestra” as we call it in the UK does not get an additional credit.
Jaikoz inserts "Concertmaster" role from MB into CONDUCTOR
Sometimes we simplify roles so we can shoehorn them into the set of tags that are widely supported, for example both Writer and Composer relations both get added to Composer field. This is what was attempted here but it looks like I misunderstood what Concertmaster meant, I thought it was another word for for Conductor not Leader of the Orchestra. So I will fix this issue that affects Jaikoz and SongKong but the fix wil be done as part of the next Albunack rebuild because that is when the mapping is created.