Impact users how? Their edits quietly disappear? The bands aren't related to the theme of the dramas/films-they were tagged in error. The tags were seemingly thought of like as twitter hashtags-ie you tweet #ASTRO #NCT or #BTS whenever you spot one of the members in anything. That is one kind of tag, but here it's been explained that it is for themes, not cast members, so taking off cast member specific tags shouldn't depend on their idol status (or size of their fandoms-many of these tags only have one or a few hits, some 100 or more because they're all very active on TV and more than that because they have fans who go far and wide to promote their presence on any/everything).
It wouldn't be a big deal to leave them on variety shows they appear on as a group, not individually-some are on variety shows strictly as actors with their costars after their drama finale airs, so it has nothing to do with their singing/dancing... For group appearances, it's still just duplicating the cast/guest list, but at least it has something to do with their music group career, not their acting ones.
If fans want all (from MDL database countries) these people are part of, they could have group profiles collating everything all the members have been on... it sounds like a nightmare, but that's kind of the end result of the really active tags LIKE EXO, ASTRO etc.