The research and findings in Horse Colour Explained are still valid. The studies done to back up the statements in that book have not been disproved. As further studies continue, more possibilities are discovered. That is true. There are exceptions to every rule. The genetic make up of animals and its evolution is built on mutation. Living things are ever-changing and our knowledge on them is ever changing and ever-growing but that does not mean that what you read on the internet (despite its newness) is more valid than published work.
Just because there are a handful of splash whites out there that are very minimal or do not have both characteristic blue eyes, does not mean you should search for splash white in every horse that has white markings. It still stands that a vast majority of splash white horses have bald faces, two blue eyes and unique, smooth-edged markings that extend upwards. This horse has none of the characteristics of splash.. except a partial wall eye, which is also frequently found in horses with other pinto patterns, not solely splash. Hence why I do not believe this horse carries splash.
Also, I never said that splash was the only pattern that could have blue eyes. Blue eyes are common in with other pinto patterns as well, and have also been seen in solids. And I also said that tobiano horses have normal face markings. By "normal" I meant, stars, blazes that end at the upper lip or no face markings at all. I said this with the implication that tobiano does not affect face markings.
The point I'm trying to make goes with the common saying: If you hear hoof beats, look for horses, not zebras. This horse has characteristic tobiano markings with a characteristic sabino chin spot. I'm saying that, chances are, this horse carries tobiano and sabino. Sure, it's possible that this horse could be tobiano, sabino, splash white, and overo! Heck, he could be carrying a silver dilute too! AND he could test negative for all of them because new mutations are discovered every day! ...but probably not.
I know that not all sabino horses test positive for sabino1. As I said in my previous post, I had my own horse tested. I tested her for agouti, extension and sabino. My horse expresses sabino markings. She has a blaze, a chin spot, high, jagged socks, and a few, small, belly spots. I was told, by the professionals at Equine Genetics Inc. that Sabino1 is the mutation most commonly found in paints, thoroughbreds and arabians that express the sabino phenotype. Drafts that express sabino rarely test positive for sabino1. My horse is half Shire. She has whatever type is common amongst drafts, which has yet to be identified. The horse in question is the type of horse that is most likely to test positive for sabino1 if he expressed sabino. That's not saying that he couldn't have some other form of sabino or that there could be another explanation entirely for the chin spot. It's always a possibility. There are always other possibilities, but considering his type, he could very well test positive and his owner could very well have some answers by getting him tested.