I don't see how app killers don't help
...
You do not know more about Android memory management than Android does.
Android isn't Windows, memory isn't 'used' in the same way. Background tasks don't tie up resources in the same manner, and unused memory is wasted memory. If it's running out, Android will take steps to recover what it needs.
I could wax lyrical about this for a while but I CBA so, just trust me, task killers generally cause more problems than they solve. If you genuinely need a task killer to stop a broken app, the problem there is you've got a broken app.
You do not need a task killer on Android. As he's found, STR's mate is wrong.