The speed of light c = 299,792,458 m/s is not a velocity. It is a construction rate — the rate at which the vacuum medium generates itself. The number 299,792,458 depends on the metre and the second, two human artefacts. Strip the units and the statement is: coherence expresses at its own construction rate. You cannot exceed c for the same reason you cannot drive faster than the road being built ahead of you. The limit is structural. c = 1/√(μ₀ε₀) is the LC resonant frequency of the vacuum — the rate at which electric and magnetic energy exchange. Both μ₀ and ε₀ follow from α, which follows from φ, which follows from the axiom.