I agree that finer classification is needed. However: if you decide to declare to a user that every individual file that might contain a virus does contain a virus, that's intentionally deceiving them. It's deciding "X% of the time, this statement will not be true, and we are ok with that" instead of building the uncertainty into the statement itself. So I don't see how this can not be considered lying, unless they believed there would be no false positives.

Until the moment where you really need that file.

Not inherently, but in this case all positives are matched to the same wording, and that wording expresses 100% certainty to the user that something in the file will harm their computer. That's a lie, because that is not what has been determined at all.

Which really shrinks when it's about presenting the known-failible process as 100% reliable, which the wording/UX seem to suggest in this case.

I can understand the reasoning behind this, I've seen it done multiple times to my own projects by the UX guys. I don't really know if it's net-positive strategy or not, but the fact that there is a lie involved at some level is undeniable. At least to those who didn't drink too much Kool-Aid and don't think the average user is too stupid to comprehend the truth, and therefore that it makes no sense to present it to the users.

I may be biased in the other direction, but every time I see a discussion about "dark patterns" in UI I get a feeling that they differ from the "light" ones only in what is the goal of the manipulation, but with methods surprisingly similar on both sides.