Creating new tags is a pain in the butt on this site (you have to go into forums and request it and shit, image boards like danbooru are way easier since you can create them from nothing, no approvals) So people will just type nyako and the tag system does not know of any cosplayer named nyako, but does know of an artist named nyako
I agree that it can be a bit of a pain, hunting down socials as source is sometimes easier said than done and the response time on that thread is annoyingly slow sometimes but these artist tags are still incorrect.
Technically we have the same option of creating a new tag from scratch but it is limited to MP25 users atm because there were concerns that not restricting it would result in every single typo becoming its own tag (which is exactly why l:English has like 50 or so synonyms and typos slaved to it), the absolute fucking disaster of rule34s tagging system is a good example of why it was probably a good decision to start limiting the tag creation to a smaller circle of more experienced users.