He could quite possibly be half Appy & just didn't inherit the LP gene, or one of his parents was half appy. My old horse was a dappled gray QH/Appy cross, but he had absolutely no Appy characteristics. That could be a reason why his former owner said he was an Appy.
His blue eyes are an indication that he's some sort of pinto as well (I'd say most probably Splash, possibly Frame). He has eyeliner, which can be a trait of both Splash & Sabino. His nose looks pink, and if you look above his eyes in the 2nd pic there is a faint outline where he's a bit darker, so I'm betting he had a big white face before he grayed out.