Torch attached to a block with no blocks under it will not break falling sand/gravel

If you have a torch attached to a block (the torch doesn't have blocks under it) it will not break falling sand/gravel.
If the torch has a block under it, it will break the sand/gravel.
The bug affect turned on redstone torch and turned off redstone torch too.

NOTE: on turned off redstone torch the falling sand/gravel create a block update, making the turned off redstone torch turn on.