The protocol specifically prohibits the appropriation of cultural property as war reparation.

UNESCO: UK National Commission for UNESCO :: Convention for the Protection of Cultural Property in the Event of Armed Conflict (1954)

If this were to be considered a form of war damage, then in principle it would be subject to reparation except that according to the 1990 treaty, Germany would not have to pay it.

FORBES: Does Germany Really Owe Greece A ��trillion In War Reparations? Probably Not, No