True, the only difference is that traditional ICBM's had a measurable fly time and a trackable radar signature meaning they could theoretically be intercepted. Hypersonic warheads are impossible to track let alone intercept. But it doesn't matter because they travel so fast there is no time to alert anyone anyway. No time to respond, No time to fire a retaliatory salvo, No time to get to a fallout shelter, no time for any sort of contingency. Its the trump card of first strike scenarios. A coordinated sortie of a dozen of these hypersonic missiles loaded with high altitude neutron bombs could wipe out all organic life in north America and leave all infrastructure and buildings intact with a single strike before anyone on the planet even knew there was an attack happening. These weapons change the nature of nuclear détente in a big way.