Golden Elf 'Sundust' is the same hybrid and therefore has the same parentage but is an awarded plant. Someone has taken their high quality or well grown plant of Cym. Golden Elf in to for judging and it received an award of some kind (not necessarily flower quality). They then were able to give it the name 'Sundust' to distinguish it from all the other Golden Elfs. You can google photos to see any difference. Chances are it has slightly different color or shape than your average hybrid.
Technically, the cultivar name has to be assigned before it is awarded, and anyone can assign one, as long as it already have not been assigned by someone else. it is simply a standard method of distinguishing among plant of the same lineage.
I saw a bright orange Golden Elf that I'd love to acquire, but it was a one-of-a-kind.