To my understanding you havent tested concurrency, and what you say is just what you think and not what really is happening. There is NO WAY different tasks using the same program can get the same storage area and or addresses. Thats what all of us already told you. When you run the transactions serially, its very likely you get the same storage as the previous task, when the system is not heavily loaded, but who cares?
If you dont beleive what experienced people and documentation from IBM tells you. why do you post on this forum?