The speed of light is the speed of light: 186,000 miles per second. However, there are some theories claiming that 'c' does vary over very long periods of time (as the universe evolves). But I don't think that that is what you were referring to here?
Maybe the flight path of the neutrinos in space-time isn’t ‘bent’ the same way by gravitation as photons, and is therefore ‘shorter’?
(Whatever the h3ll that means...)