[magicalhippo]

The experiment is described in this[1] article. Relevant quote:

The detector is positioned on the beam collision axis line-of-sight (LOS) 480 m from the ATLAS collision point (interaction point 1, IP1) in an unused service tunnel, TI12. [...] A huge number of neutrinos are produced in LHC collisions via hadron decays, and their flux is collimated along the beam collision axis.

So what they did differently is to place the detector in a spot which has much higher neutrino flux than your average spot on earth. Thus the small detector volume is compensated for by having more neutrinos pass through it in a given time.

[1]: https://arxiv.org/abs/2207.11427