A falling block entity falling down a 1x1 shaft will clip a torch mounted on the shaft wall. This has been confirmed with:
Falling Sand
Falling Gravel
Falling Red Sand
Falling TNT (ignited TNT)
You can clearly see in the video that I placed the gravel on the same wall as the mounted torch, so there's no question about whether I was a block off.
I've tried to understand, but as far as I can tell, this works as intended. Gravel and sand will pass through a wall mounted torch to fall to the ground below it. When the torch is adjacent to a floor, the gravel and sand drop as items instead. Please provide more details if I'm missing something.