Yeah, that's a bald-faced lie, and indicative that you haven't actually done any exploring to know what you're talking about. I've found a number of high-level loot chests in offshoots from the main path. The devs particularly favor putting them under trees and behind bushes in the "green" dungeons that contain animals and spriggans, probably because the flora provide more natural ways to hide them.
If this were true you could name the dungeon(s) that do not end with a boss, loot chest, and shortcut back to the entrance.