Well, if that drawing is representative of what was meant, it may or may not be legal. If only one of the balls is sufficient to trigger the next task, moving the other would almost certainly be considered a parallel task. However, if both are needed, then you're probably fine. Again, this is definitely not an official clarification, submit those through soinc.org (although for something like this you might not get a response without more detail/specifically addressing a confusing line in the rules). In any case, I probably would design something that is more conservative and leaves no question in the event supervisor's mind.