This does not make sense.

Chase is functioning as an OTA, a ticketing agent, of the ticket. They do not have the ability to override the rules of the ticket itself. If they sell the flight on DLs behalf, and the ticket is none-refundable, the credit would contractually be linked to the ticket. f you call DL, they would be able to see the credit. They may be contractually unable to re-ticket it for you because its an agency ticket, but that money doesn't actually belong with chase. Its with the ticket and DL. (I suspect this is why you have to call Chase to rebook).

If however the ticket was actually refundable, Chase could hold the funds under their own set of BS terms and conditions, but the ticket in Deltas system would show refunded.

Expedia pulls this crap with change fees too. One of the myriad of reasons to never use OTAs. On the rare occasion Ive had to book with them, Ive actually called the airline directly, verified the proper change rules, then thrown them back in Expedias face and often they would cave.