Soldier Eligibility for "Improve Combat Intelligence" in X-COM 2 WotC

Question

One of the Covert Actions available in XCOM 2 WotC allows to to improve a soldier's Combat Intelligence, however there is no indication of why a bunch of my soldiers are not eligible for the action.

There's no rank requirement these soldiers don't have, they are not at the apparent highest level of Combat Intelligence either. Did I miss a hint about why most of my soldiers are not eligible for those missions? Is there some hidden requirement?

Answer 1

I think I figured it out. All the Faction Soldiers are apparently ineligible — as are Psi Operatives and Sparks. With the latter two it kinda makes sense since both work a bit different the usual soldiers anyways.

So eligible are just the base class soldiers which have not yet reached Savant level combat intelligence and who are not tired or wounded — and of course fulfill the prerequisites of the Covert Operation itself.