On GitHub it was said, “This can help with reducing bodies passing through each other in many cases.” The word “Help” does suggest it's not a definitive fix to this problem, but the demo shows a dramatic improvement…
https://brm.io/matter-js/demo/#substep
I filled it with lots of tiny bodies and they rarely went through the stick. When I thought that one of the bodies did go through the stick, I had trouble seeing it happen again to confirm it was actually happening — but even AAA video games have trouble with perfect collision detection.
Just see the Backwards Long Jump in Mario 64. 
It seems to help A LOT! 
Just look at the current state of Hype…
Stick-Test.zip (10.9 KB)
The square goes right through the stick with just some basic gravity.