I understand it was a result of an error in the labelling of some imported budwood.
Both varieties were ordered and when the budwood arrived, it was propagated and shared with major distributing nurseries in Australia.
It takes a few years to get to know a rose well enough to suspect an issue with the identity and by the time nurseypeople and other growers realised they had two Celines and no Desprezes, the rose had been distributed widely in Australia under both names.
The correct Desprez a Fleur Jaune has since been imported but I’m not certain who sells it.
Good luck!