Well, there sure are ways of using a knife that result in less blood being on the knife-wielder. I don't know what "sloppy" meant in the original reports, but I have assumed it means there were at least bloody glove prints. What a killer might want to avoid is arterial blood spurt, but if the killer were dressed properly, I suppose even that wouldn't matter that much.
It does raise the issue of where they went to clean up. But if the killer knew what he was doing, anatomically, he might have been rather precise (what Mr and Mrs G have said makes me think that's the case, but who knows). At any rate, there are more and less precise or sloppy ways to use a knife. I don't think anyone ever said the crime scene was "clean."
I agree it's really hard to know what "sloppy" means in this context. First of all, it was the first stabbing murder in living memory in Moscow, so it was going to look "sloppy" if that means "lots of blood" (odd choice of word, still), When I first saw the word, I figured it meant bedclothes tossed everywhere, things knocked over, items of the killer left behind, etc. I suppose this could still be true. It's possible they had some item that gave them the killer's DNA right away. Perhaps that's how they compiled their "believe not to be involved" list but they still don't know who the perp is (or the DNA is not enough to make the case).
If we're still in this holding pattern in February, my heart is going to sink.