FWIW, after I gave Klarna a sneak peek into my banking account several years ago, I did a GDPR/DSGVO information request a few days later, and according to that, they did not store the transactions they had access to.
Not sure if the information was truthful, of course.
Nobody is auditing nor policing those GDPR SAR responses, so there's little reason to be truthful. The most likely explanation is, short of actual malfeasance, that the ticket of "include transaction data or data derived from it into GDPR data exports" is rotting in the Jira backlog to this day.
Not sure if the information was truthful, of course.