This takes the top event in the queue, and retries it every 'interval' (which is defined in an Engine Control Value, defaults to 30 seconds).
So yes, it blocks all following events until it completes and stops being a retry.
What you could do is much simpler. In the Input Transform policy set, look for the operation add-association since that is when the object is successfully added to the connected system.
Then do your rule B stuff.
Unless you mean two different objects A and B, that are otherwise unrelated. If so, would let object A logic go through, and when you see object B come through then do the work on object A that is needed.