Yup, that is correct, JustFrozen. Also, when we add up to 4-5 ppm of ammonia, when the cycle has finished, the 4-5 ppm of ammonia that our bacteria are processing is enough enough ammonia to colonize enough bacteria to handle a full bio-load of fish. In other words, if done properly, a completed fishless cycle will allow the person to add the full stocking of fish to the tank without any worries of an ammonia or nitrite spike. Now, even though the cycle is finished and you have added fish, you should still monitor the water parameters for a week or so, just to be on the safe side.
But like JustFrozen said, during the nitrite spike, if we were to continue to add up near 5 ppm of ammonia, the nitrite would be off the charts. So, the 2 ppm is enough to keep the ammonia bacteria alive while the nitrifying bacteria can catch up, while keeping nitrite at a more controlled and easy to measure level. Once nitrite begins to drop to 0 ppm, you can than start re adding ammonia back up 5 ppm.
-FHM