I have no cause to argue your points , but I did find out the probable the causes of wear.
I was talking to a shop owner who has sold mopeds for 50 years.
He said that its the piston skirt wobble that causes the lower cylinder wear.
My theory on whether the fuel charge doesn't get to the upper is just that , a theory.
Either way , We have twice measured the wear with our micrometers and after installing a better cylinder , the bike starts up instantly and runs fine .