besides the “video” flag, some good reasons for seperate recordings is that videos will almost always have different relationships than the audio recordings, such as video producers, editors, directors, etc. and songs can have multiple music videos too (official or not), which are often distinct enough from each other to also warrant different relationships
also, whether a recording on a release is a video or not is an important distinction, at least in more traditional releases, like this Enhanced CD which includes a video as a bonus track (quite common).
also, I wanted to note that usually music videos should get a release. I believe we’re moving away from simply standalone recordings, since there’s a lot that can’t be adequetly represented that way (release dates, labels, video thumbnails, and more)
there’s currently discussion over here about how to handle what, if you’ve got anything to add~