All variants of block 161 (leaves2) besides 161:2 are named Acacia Leaves. Dark Oak Leaves placed by the player change to 161:9 so that it will not decay, however, the name is still "Acacia Leaves". Language is set to English (US)

To reproduce:
1. search and place "dark oak leaves" from the creative menu
2. throw away the leaf block in your inventory
3. pick block the "dark oak" leaves and notice it is called acacia leaves.