Well, the point is that there was a neutrino burst coincident with SN87a. So if there was one 4yr earlier, too, then you'd have to explain how the same event produced two bursts of neutrinos with different speeds, while within the burst they apparently had exactly the same speed.

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.)