They make the plan as a training exercise, not something they actually think will happen, but if they ask a new planner to plan a war with China he's probably thought a lot about it and you learn more about what plans he's read than what unique and out of the box thinking he has, if you ask him to make plans for zombie outbreak or idaho rebelling or an alien invasion in Montana you get unique answers, so they have thousands of plans that no one ever reads again but it's less competence and more " 1999 q4 training exercise"

vastly overestimating the competence of the people

oh homey. tsk. you've mistaken 'doing some planning' for 'competent planning' and (critically) PREPARING for idaho to evaporate suddenly. Trust me, books of PLANS we have. Plans we have prepared for, prepositioning potato supplies, figuring out where we can outsource our hyperchristian conservative militia types - you know, idaho things - no, we haven't done that. There's planning, and there's preparation. One requires a few flag grade officers to pontificate and argue, and some field grade officers to type for them.

The other requires logistical competence, funding, training, and careful analysis. We don't do a lot of the other.

Are you saying competent military planners are concerned with the sudden disappearance of Idaho, and also think the biggest problem that would cause is that the flag wouldn't correctly represent the country anymore? It's plans for the things that actually do happen (or almost happen) that are few and far between.