The wooden hammer is very OP, but it doesn't update blocks in a 3x3 area. Instead, it only updates the blocks around the one you mined with the pick, causing random holes that should be filled with stone to be filled with air), but when you update said blocks by mining the block next to it, or right clicking the block, it fills the gaps with the correct block. This is caused by the anti-xray plugin, as far as I can tell. Same goes for ores. Whenever you mine, you can see random stone blocks not get mined, and guess why? Because they're not stone, they're just non-updated ores that the wooden pick can't mine.