It’s just opinion. All we can really do is guess at this point. I haven’t seen any really convincing arguments about how we were supposed to know palimpsest and abscissa beforehand so I looked at it the other way. They were just sort of what each section reminded him of in development so he used them as keywords. If he did that for at least half the sculpture and potentially K3 as well then it seems reasonable to suggest he was consistent for the whole thing.
This is what he said when I asked him about the keywords:
Kfan: “Palimpsest and abscissa carry connotations of teaching/classrooms, is there any credence to this association and what other context could they have?”
James Sanborn: “I liked the words and their definitions”
(ref: http://kryptosfan.wordpress.com/2013/05/30/jim-sanborn-answers-kryptos-questions/)
He had to re-send his answers because our intermediary had issues so his original answers may have been a little more forthcoming.
TL;DR Not so sure but some assumptions have to be made.