Ich finde den Regeltext gerade nicht, denke aber dass deine Leute recht haben. Ausserdem ist ein 1,5 m Schritt keine Free Action.
EDIT: Vielleicht verwechsel ich da etwas bezüglich
Hampered Movement: When conditions don't let you move as quickly as your speed would normally allow, your movement is hampered. When a creature enters a square where movement is hampered, it pays at least 10 feet of movement instead of the usual 5 feet. When moving diagonally into a square where movement is hampered, a creature pays at least 15 feet of movement.
Uneven surfaces, slippery surfaces, obstacles that leave you room to pass but require you to climb over them or detour around them, thick vegetation -- all these can hamper your movement.
A creature cannot charge, run, or take a 5-foot step when its movement is hampered.