This is an old gem dating back to the MX system, which was actually much newer than the Minuteman III system at the time. [0]
MX was deactivated in 2005 per SALT II. [1]
They moved the enhanced RVs from MX over to Minuteman. [2]
[0] https://www.youtube.com/watch?v=2a1acYZ93yc
[1] https://en.wikipedia.org/wiki/LGM-118_Peacekeeper#Retirement...
[2] https://en.wikipedia.org/w/index.php?title=LGM-30_Minuteman&...