Feels weird to talk about the "can neither confirm nor deny" stuff when the website for the Warren AFB and 90th Wing so plainly say that they have and operate ICBMs.
https://www.warren.af.mil/About-Us/Fact-Sheets/
https://www.warren.af.mil/About-Us/Fact-Sheets/Display/Artic...
Maybe it's something like some of the missiles have no warhead on them, and you don't know which ones.