I would not be suprised if a koi showed up with those markings but the article says that the fish were artificially fertilised from Ayu and Koi and that is pure BS.
Here is why,
Koi are a type of carp;
Species= carpio carpio
Genus= Cyprinus
Family= Cyprinidae
Order= Cypriniformes
Ayu are a type of smelt;
Species= carpio carpio
Genus= Plecoglossus
Family= Plecoglossidae
Order= Osmeriformes
In order to hybridize, even artificially the animals have to be in the same family at least.
Crossbreeding a smelt to a carp is the equivalent of cross breeding a chimpazee to an armadillo.
It ain't going to happen