Banana Pudding

I'll first say I think this is more about semantics...but it has also driven which approval chain to use. Givens: Cost Reimbursement contract. Cost overrun is imminent. Pretend you're just looking at the FAR. Not DoD or DFARS....which has a LOT of SOPs for Undefinitized Contract Actions (UCAs). When I pair the last few words of FAR 16.301-1 "...ceiling that the contractor may not exceed without approval of the contracting officer" with the language in FAR 52.232-20 (Limitation of Cost), it sure seems that the Government has the option to modify existing cost ceiling after negotiation. Now, if the modification remains within the scope and under the terms of the original contract, I would not call this a "contract action", and thereby not associate the "UCA" term with it. I'm pulling that logic straight from FAR 52.232-16, which does a solid job defining what a contract action is. Problem is that clause would never apply, given FAR subpart 32.5 (where it is prescribed) does not apply to Cost Reimbursement contracts. I have not found success in GAO discerning any difference...they call everything not defined a UCA. Any thoughts?