Just throwing my two cents in…
I believe most of the videos in question (Hololive covers) should be on a release of some sort, since they’ve been released on a streaming platform, namely YouTube. Whether a Single, Other, or “video single”, I’m not 100% decided on.
For example, in the case of Ina’s “VIOLET” above, I might propose adding the video to a new release under the release group for the single, tagged as “Promotional”, since it’s promoting the release of the single.
Also, I’d like to note that most but not all quote-unquote “Official” Hololive releases have a true video release, just look at Gawr Gura’s REFLECT released a couple months earlier. It’s got a streamlink and everything, but the “Video” on YouTube is just a still of the release cover. I might still add a “Promotional” single if the video was released earlier, but I’d say just use the audio recording on the release in this case and don’t make a video recording just for a still-image “Video”.
In the case of the covers, I think adding a URL begin date is cool, but it’s a feature that almost nobody (including me, until a couple days ago) knows about, (though possibly not for long)
And anyways, think of the taggers, how will we they get release dates tagged without a release to pull it from? Release dates are very important to us them! 
(jk, jk…)
To my eye, the Hololive gals, (and maybe Holostars too) have, in general, two parallel “standards for how they do releases”, one being through music streaming services like Apple Music, Spotify, etc, and one of them being music videos on YouTube. In every case I’ve seen for this group, most (if not all) of their musical content is said videos. Just look at Airani Iofifteen of Hololive ID, she’s posted several cover songs on YouTube, and I don’t think they’ve been released any other way.
As a total sidenote, I personally would likely add these as events, possibly even standalone video recordings for the whole stream, related back to the event (at least if they’re archived, but this is getting a bit off-topic)
…okay, that was probably more like 32 cents, lol
it’s nice to see some Hololive fans in the forums, btw~ 
Yagoo is best girl~