Right you are. The FAQ addresses this:
Behind Enemy Lines
Q. May an infantry unit move three hexes on a beach when playing the 'behind enemy Lines' card?
To avoid endless debate about this card, the original intent of the card was that the infantry unit's movement would not be restricted by terrain but terrain battle restrictions would still apply. I failed to word this clearly on the card. The card should of read that Terrain movement restrictions do not apply but battle restrictions do still apply.
Terrain features that cost more than 1 movement only cost 1 move when an infantry unit is ordered on the Behind Enemy Lines card. An example of this is for the Omaha Beach scenario where moving up a bluff for an infantry unit from the beach is a 2 hex movement. Moving up or down the bluff in this case will only cost 1 move for the infantry unit when ordered on the Behind Enemy Lines card.