Then again, it's not a proper Cold War strategic game theory play unless you're banking on your enemy to hesitate due to the unusual nature of the attack. SLBMs scream first strike, while a few birds out of many launching from farm country in the central United States in sequential fashion, not so much.

That said, I'm not sure what would have consituted "twitching" after Soviet C&C is wiped out, and if I was a planner at the time I don't think I'd want to find out. It would likely have been prudent to immediately follow up the decapitation strike with complete annihilation of Soviet nuclear retaliatory capability. Every deployed Soviet boomer accounted for and shadowded, with firing solutions computed. Every missile silo targeted. Presumably strategic air bases would be targeted in the first volley, though there would remain the possibility of strategic bomber patrols already airborne.

First strikes are really messy and entail a ridiculous amount of risk. Considering the stakes, it's no wonder neither side ever tried.