A great deal of what Snopes does (particularly in recent years) is much closer to "opinion" than "fact", especially when they start labeling things "mostly false" or "mostly true" or whatever. You can't do that when you're dealing with actual facts.

Yes you can. What in the world? You can definitely say something that is partially true. That's what conspiracy theories are built off of: a tinge of truth.

"The sky is blue because other stars reflect blue light onto our atmosphere." How would you rate that, given Snopes' scales?

Do you have any specific examples where there was a concise yet opinionated decision on any published articles from Snopes that don't rely on hard evidence for their conclusion?