Here are the rules (from french rules):
Draw as many territory tiles as the number of players and place them face up adjacent to one another. In a 3 or 4 player game each tile must be adjacent to at least 2 other tiles.
Hope that helps.
That got lost in translation for English version. It just says that each tile must be adjacent to two others (no “at least” either). Hence the confusion for 2p setup - it implies that you should use 3 tiles.