I see the red that you are talking about, and seal brown horses seem to have darker legs, but I'm confused too...
I was wondering if his socks could possibly make his legs look lighter (obviously they can make them white, but make the dark points not show at all?) and can a liver chestnut have tan on its soft spots? In the second picture and last picture he looks like he has tan on his flanks and other places.
I'm not trying to second guess you, you sound like a pro! Just trying to learn