I am not taking up for the tech in the picture, he shouldn't carry an aluminum ladder for any reason, period. But, if you look closely, the ladder on the right side of the rack is a yellow (faded) Werner fiberglass ladder, you can even see one of the hooks in the front.
I always carried five ladders: 32', 28', 16' extensions and a 8' step, all fiberglass. I carried a small plastic 3' kitchen type step ladder for basements...never carried an aluminum ladder for anything. The only amuminum in my truck was wrapped around my lunch!