We don't want a "commitment to jointness," we want to identify fighting ability within the joint force.
It's different cause you can be committed and suck. And you can appear apathetic or obtuse, but turn out to be brilliant when put on the "X." It comes down to performance and merit.
But to help you out, JPME II, taught at the War Colleges, where you were a "department chair," does have a CJCSI defining the expectation of a joint qualified officer. This instruction is where all joint learning outcomes are derived.
More than 20 years ago, when I was a department chair at the Naval War College, I was told that faculty would be evaluated on their “commitment to jointness.”
I asked my boss, a decorated combat veteran, what that meant.
He said “I have no idea”