Release group artist credits don’t look redundant to me, the rear might have credited them separately to emphasize the role of にしこ on the release. Either way, the rear is a more reliable source than the retailer so I’d leave it as is.
I am not so sure if track/recording artist credits should be given to the arrangers or follow the release group. The classical music guideline has this to say, tho would it apply to doujin releases as well?
> The Recording Artist field should contain the most important performers who appear on that specific recording
If someone knows more, please correct me!
(edit) After having read a thread discussing what is considered classical music I figured that classical style guidelines wouldn’t apply to this release or doujin music that has “classical influences”, it’s still primarily doujin music, my bad!