I wouldn't necessarily rely on Pet Keen for reliable information. For instance, pink or red eyes are not rare (and the Californian pictured in the section on pink eyes has that lack of color due to the partial albinism of the himalayan genes blocking pigment in the eyes, not a dilution of normal brown, which generally results in blue or blue-gray eyes). And marbled eyes aren't really a "genetic disorder," unless you consider all the various mutations that create different colors and fur types to be "disorders."
Much better resources, in my opinion, are sites like
https://www.raising-rabbits.com/https://arba.net/recognized-breeds/and of course RabbitTalk.com
Those are sites where you'll find accurate information about rabbits especially applicable to the U.S and Canada, though RabbitTalk has good resources regarding European rabbits as well.
Importing rabbits from Europe and elsewhere is complicated and expensive. If someone brought Hulstlanders into the U.S, it's fairly unlikely that a rabbit that came that dearly got sold as a pet or was left to roam. As far as I've heard, Hulstlanders are accepted in the British Rabbit standard but are pretty uncommon even there. Maybe
@MsTemeraire has more information about them. But Hulstlanders are a recognized breed, meaning they are no longer considered a hybrid (or more accurately, a crossbreed). Most breeds can be traced back to other breeds that were used to create them; for example, New Zealands may have been bred from Belgian Hares and Flemish Giants, among others.
Also, Hulstlanders are Vienna whites, and given the coloration on his nose, Nanners is more likely an ermine (non-extension chinchilla) rather that a Vienna-based blue eyed white. It seems more likely that Nanners is a crossbreed of some sort. Given his size - which appears to be somewhat more than 5-7 pounds - New Zealand White carrying red and American Chinchilla, both common enough, would be a good guess at some of his forebears.
