I don't think that's true. The energies of the neutrinos they are looking at are relative low (less than 15 MeV), and according to https://journals.aps.org/prd/

I don't think that's true. The energies of the neutrinos they are looking at are relative low (less than 15 MeV), and according to https://journals.aps.org/prd/pdf/10.1103/PhysRevD.60.053003 https://journals.aps.org/prd/pdf/10.1103/PhysRevD.60.053003 the positron is isotropic around 15 MeV and is only forward pointing at much higher energies.