Maybe this one helps. From '59 or early 60s.
The idea is to get the burning to develop maximum leverage.
When a burn that continues to grow after the piston is further down the hole, that heat goes into the cylinder walls.
Pressure from a burn can be used to help get the exhuast moving out of the cylinder, so its not all bad. I think some guys are calling this the 5th cycle in 4 stroke engines.