I don't know where he's getting this from but common sense tells me that you work from the top down to save getting drips or splashes of paint on freshly painted walls.
He is a stubborn bastard at times and is insisting that he will do the picture rail last. I know there will be paint splashes on the nicely prepped and painted (with Farrow and Ball Ammonite) walls. What's annoying is that he's put loads of effort in and has even masked off the picture rail, although as the ceilings and above the picture rail are white I have no idea why he's felt the need to do this as he could have just painted the bloody ceiling then picture rail and it wouldn't have mattered if he'd gone onto the walls slightly as he'd be painting the walls afterwards over it anyway!
There is no telling him. He will get a cob on if there are splashes on the wall afterwards and I point them out.
Has anyone here painted a room and done the picture rail last, in satinwood (which I know is drippy anyway) and not made the walls look like a bloody constellation?