Its a simple and not that important bug.
But the Block Breaker cant break snow layer.
Everything else seems to work fine.

Well, it wasn't exactly bug, but kind of design oversight that caused block breaker to break only blocks that could be harvested with pickaxe (i.e. would drop item). And snow isn't harvestable, since it drops snowballs only when broken with shovel.

I decided to change that logic and allow breaking incompatible items (change in snapshot 520). In next version there will probably be way to select correct tool.