Could a physicist clarify whether neutrinos could travel at different speeds in vacuum like any 'normal' particle, or are 'fixed speed' like photons. We could well have had several waves with the bulk arriving at c-epsilon and no one bothering to check outside the expected time frame.
If neutrinos have mass, they can travel at any speed <c depending on their energy, like any other massive particle. Of course, the upper mass limit is quite low, so even with very little energy they will go very fast.
(Edit: In fact, the arrival interval of those neutrinos puts an upper limit on the neutrino mass, because the larger the mass, the more different the speed and the more dispersed the arrival of them at Earth.)
It could be some phenomenon similar to what we see in emission spectrums, where a pure source can emit photons at multiple precise energy levels. except that in the case of particles with mass(apparently neutrinos have a mass) this would result in a difference in speed. Not a big enough difference to be noticed on 700 km , but enough to make a 4 yr difference on 170kly.
Of course this is still wild speculation without much background.