The bug

The brush can target through some blocks that have no collision. However, the visual outline box will still show for the first block you see, rather than the one the brush interacts with.

How to reproduce

1. Locate tall grass
2. Attempt to use a brush on it

Expected results

As the brush is being held, the block behind the tall grass would be brushed instead, with the outline box changing to show this, much like how light blocks can't be targeted if not holding the item.

Actual results

The block behind the tall grass is indeed brushed, but the visual outline box is still for the tall grass.