So, hear me out. I'm a dumb experimentalist that remembers a tiny bit of QFT from my master's.
IIRC, in the SM Lagrangian the fields don't have any explicit mass term due to symmetry. The masses come instead from the interaction with the Higgs, and it is only when re-writing the Lagrangian with respect to the non symmetric VeV that the mass terms pop out.
This would mean that from the point of view of the 'unbroken' Lagrangian, the lepton fields all have mass zero, and therefore their excitations travel at the speed of light. Since the mass term is a consequence of the interaction with the Higgs field, how wrong is it for me think that the slower than c speed of normal particles is just t