Two Stroke Engine Surprise!

On 2 stroke engines, there are normally ports (openings) within the cylinder walls to let the fuel mixture in and the exhaust gas out, other than on a 4 stroke engine where the valves cause the absence of these openings within the cylinders. The pistons and therefore the piston rings run over these ports while the piston moves up and down the cylinder. The piston rings travel inside the piston grooves. The piston ring openings could end up earlier or later within those ports causing the ring to open slightly, stucking at the edges of the ports destroying the ring causing excessive wear or even an engine failure. To avoid travelling of the piston rings within the grooves, 2 stroke pistons normally have piston pins to lock the rings in a dedicated position to avoid the ring openings to run over the ports. Surprisingly, this Velosolex 3800 2 Stroke engine from 1968 doesn’t have and never had pins on the piston to avoid this. Why did it run for decades without troubles? Why do original replacement pistons don’t have these pins? Any thoughts?