You know what, there’s a small chance they would if they knew. But let’s say the Pentagon stopped all silos and kept it hush. Russia and China would never know whether they stopped or where remaining ones would be.
If nothing else*, they would notice the changes in budgeting. The amount of money we spend every year on maintiaing the nuclear arsenal is staggering. if that suddenly paired back or chanced it’d be basically public information. Maybe not specifics, but there’s enough detail to know what’s being spent on what.
MAD only works if the other party thinks you can, and you will. Also, once you start using MAD it’s almost impossible to stop.