We're laughing at the ladder set on the van roof ... which actually might not be such a bad base. Far worse is the use of another ladder as a scaffold plank.
I believe they're just using that ladder as a safety rail/work platform. If you look closely, there's a typical solid siding platform to stand on just below it, with that ladder mounted about waist height.
Though, the way they placed the (van) ladder makes you wonder just how they get from the ladder to the work platform! I hope they aren't crawling over that ladder- it's one thing to lay sheets of siding on it, but there's no way it can safely support a man's weight.