Another take. KC deal only applies to info feds know about already. In my understanding, only for the Page FISA. KC still on the hook for anything else, and it's in his best interest to come clean on all of it.
IOW, if feds hammer him for the first charge, KC may be reluctant to give up more, whereas a sweet deal on first charge motivates KC to fess up to more.
https://twitter.com/shipwreckedcrew/status/1296287814955368449