Yep, pretty common, most people don't label it as "sooty flaxen" though. Most would just call it regular "flaxen" or some wouldn't mention the flaxen at all.
Smrobs, another novice horse color question :P lol.... why isnt his tail like that? Is it sort of like a "spots" of sooty on the horses body. Randomly? Like a white spot on a horse's mane will make that part white? Is it like that?