A buckskin is basically a dun without the black points. Just like brown is basically bay without the black points. Two seperate genes. If it was a "dunskin" it would be a dun...I mean, honestly. It's like those "Designer Dogs" that are "Labradoodles" or "Goldendoodles." And now its invading the horse world. Ugh.
Another example. Tri-Colored paint. Eh. No again. It's a Bay Paint. No such thing a tri-colored, no matter how cool it would be.
There is a lot of misinformation in this post - It might pay to check out the facts before posting.
A buckskin DOES have black points. The cream gene cannot dilute black hairs in it's single form - So only the red coat on a bay is diluted, leaving the black points. Only in it's double form can cream dilute black hairs - If on a bay base, it becomes a Perlino, similar to a cremello but with slightly darker mane and tail.
A dun has the diluted coat, same as a buckskin, but what makes it a dun are primitive markings. They can be quite pronounced or almost invisible. These are leg/wither barring, a dorsal stripe, and counter shading. They may have some or all of the primitive markings.
It IS possible and documented via genetic testing that horses can carry both one cream gene and the dun gene, genetically making them a dunskin.
They generally look just like a buckskin, but may also show some or all of the primitive markings.
The only way to tell for sure is getting them tested.