Why do people think that cardinal will/should not be compensated by DL/AF?

If I read this right, the PNR was updated to have the correct names, and that is what the OP saw. That the backend ticketing process failed is not something a passenger can be expected to understand or detect.

Clearly this was a failure within DL/AF to properly ticket. Exactly where does not matter.

Though I would agree that OP is not legally due damages past the ticket refund, as a practical matter they do generally reimburse for reasonable costs incurred due to their failures.

On a side note to myself, always check the e-ticket not just the PNR :-)