Mangrove roots can replace bedrock when growing a mangrove tree

In some situations when growing a mangrove tree, the roots can replace any block including bedrock.  As far as I can tell it can replace blocks exactly 1 block away from the propogule horizontally, and it is more likely to occur the more blocks that are blocking the path of the potential root in that direction.

To reproduce:

1. place a mangrove propagule, with enough space to grow on all sides
2. on one of its sides place bedrock right next to it stacking up vertically
3. bonemeal the propagule, it doesn't work 100% of the time but it will break the bedrock after a few attempts