Personally, I like to be in control over how much ammonia is being dosed into the tank.
Ie I am dosing a known amount of ammonia at 2ppm, looking for when the bacteria colony has developed sufficient to metabolize that challenge to 0 ammonia, 0 nitrites within 24 hours of dosing.
Other methods of adding ammonia such as ammonia leaching from aquasoils, or as a response to fish food decaying in a tank or from the aquarist adding urine to the tank does not give you the knowledge as to how much ammonia the beneficial bacteria can handle per day.
Ie I am dosing a known amount of ammonia at 2ppm, looking for when the bacteria colony has developed sufficient to metabolize that challenge to 0 ammonia, 0 nitrites within 24 hours of dosing.
Other methods of adding ammonia such as ammonia leaching from aquasoils, or as a response to fish food decaying in a tank or from the aquarist adding urine to the tank does not give you the knowledge as to how much ammonia the beneficial bacteria can handle per day.