True. But the last couple of strategic arms reduction treaties (SORT and the current New START) didn’t, I believe, require either side actually to destroy any warheads. They just had to take them out of deployment (and, according to wikipedia, out of ‘reserve’, whatever that means). It could be that the US has warheads in some kind of (non-reserve) storage, which might well be at Livermore. If the missiles are able to carry MIRVs then arms reduction is easy - you just take as many warheads out of each missile as you’ve agreed to. But it might not take long to put some of them back.