[jptlnk]

I haven't read the full article yet but the abstract has some hints: I think what they're doing is leveraging the fact that they know where and when the neutrinos were created to narrow down the search in the actual neutrino detector itself.

Because they can see the associated muon, they know when to look for a correlated neutrino signal.

Between that and the extremely hot source, they can get away with a relatively small active detector volume.

Again that's just based on my reading of the abstract, I need to see the full article to validate that guess.