Our current tagging practice as regarding VShojo is just the logical conclusion of our tagging practice for the tag when the company was still around, and can be found for other entities like Densetsu.EXE, BEASTIEZ, and VchiBan.
Even when taking into account that they were still independent entities while still part of VShojo, they were part of a broader brand (so at bare minimum, you can't nuke the tag, because you have art with VShojo branding in it). But imagine telling someone "hey if you want to search for fanart of this vtuber when they were part of vshojo you can't, and you can't rely on when it was uploaded either because someone could've uploaded pre-vshojo fanart while they were part of vshojo, or vshojo-era fanart after vshojo shutdown, so fuck you", they'd probably call you insane. People searching for VShojo wanted an easy way to find fanart of its members without having to do multitag searches involving each, as that's how people handled VShojo's tags elsewhere.
But that then runs into the perennial issue of copyright tagging - deciding on a main copytag. For most cases, it's simple, but the simplicity causes issue here, because by its logic, we'd tag all VShojo members' fanart as VShojo because they were members, including pre- and post-VShojo. That'd cause a lot of tag changes, so that'd be incredibly impracticle. So, with Virtual YouTuber being recognized as a generic-copyright tag, the solution was reached to tag the copytag based on when the art was made. Some people dislike this solution, because it puts a bigger burden on taggers to figure this out, but I think as long as that info is clearly presented in wikis, it's fine. When you have folks like Kaneko Lumi, it's kind of a necessity.
So, as ggraphy said, keeping the status quo is the ideal position, and one which even the current site admin agrees with, having helped clarify the conditions listed in the wiki. Nuking the VShojo tag has no benefit to us.
This in turn brings us to Suisei - everyone fucking associates her with Hololive, and everything she does is tied to hololive Production, including Studio Stellar. Her first post on Danbooru is from after she joined Hololive, and I don't even think she even has pre-Hololive fanart upped (which would have to be tagged as indie). If you told someone that "she should be tagged with indie virtual youtuber because she owns her own IP" they'd probably yell at you.