Like @reosarevok said, just because they never got a professional release, we don’t have anything against those eight cut recordings – and even if they’re rough, we have the “Demo” secondary type for a reason. Moreover, they wouldn’t even need to be in a Soundcloud playlist; the mentality I’ve been using is that unless it’s a particularly rough sketch, is obviously part of a set (same upload date, cover, etc.), or is a music video, something uploaded to there or YouTube counts as a single.
Recorded and did nothing with? Yeah, that’s somewhat debatable. Recorded and tossed on SC? That’s a perfectly valid release.
And again, if you’re intending them to record a better version in the future, then that seems like a “Demo” release to me. If you’re just putting it there as a “Well, this was a fun project but I’ve lost interest and won’t be refining it any more”, that’s maybe a standalone recording rather than a release, but it still has a place in the database.
I don’t think anyone here is advocating premature entity addition, but we don’t impose artificial “notability” requirements, either. Does something exist? If so, then why is it any less or more deserving of mention than anything else? From a more pragmatic perspective, one of the most common (though definitely not only) uses of MB data is for tagging files; people don’t just buy the most common or most well-reported release, they almost seem to track down the most obscure artists and the roughest demos and WIPs. Saying we won’t support that would be one of the more arbitrary ways we could come up with to turn people to other services.