Almost there....
Remaining problem: when I compare the (new) write time of the version.lisp-expr file, against the component-operation-time, they are equal.
So most likely, I'm getting that time because the check is being done while I'm updating the component-operation-time, or the component-operation-time is updated at the start of computing the action stamp.
So I feel very close, but am still wandering in the wilderness....