Have a similar issue but with an airline that isn't known to be involved in this POS caper. I organised SIN-FRA-SIN on QF in D for my parents via their TA in Singapore. They're waitlisted on both segments, despite FRA-SIN showing D9. And this is a regular D return, not a oneworld global product.

edit: the differing availability via various GDS has got me thinking. TA is on Abacus, QF is on Amadeus. Might get the TA to contact QF directly.