Vocaloid songs very commonly receive covers and parodies of their music videos. For example:
I've always excluded and removed the Vocaloid or related tags (UTAU, etc) from these if they were parodies with other copyrights (vtubers, etc) without actually having Vocaloid characters. My reasoning is that the song tag itself should suffice to indicate what is being parodied. And as a Vocaloid fan myself, I am personally not interested in seeing vTuber/etc parodies whenever I search the Vocaloid tag, rather I expect to view posts specifically with Vocaloid characters.
However, I do see that @TheGamingRodent adds the Vocaloid tag to Rabbit Hole (vocaloid) posts, and even re-adds it after I removed the tag and explained my reasoning in comment #2506547. I asked about his reasoning, and he simply replied that they were part of the copyright, and he planned to create a BUR to add the tag to all song tags. I personally don't agree with this for the reason I gave above. I believe if anyone really wanted to view all Vocaloid-related posts, they can simply use the wildcard *vocaloid*, while those of us who do not want to view song parodies will not have to. But I thought I should ask for general public opinion instead.