A heavily planted tank is not already cycled. That's misinformation, plainly, and serves only to confuse newbies. There's no sense in having a silly argument about something so common and modern in this hobby. People fishlessly cycle tanks in order to provide the most humane, comfortable and pseudo-natural environment for their livestock.
Plants use ammonia as food. That doesn't mean bacteria are present to consume waste as would occur in a cycled tank. No, the tank is not cycled just because plants are present. Just because plants are in a tank doesn't mean all the bacteria necessary for a tank to process a full fishload outside of what plants use are present.
Yes, plants using ammonia as food can and do mask things. Just because your mass of plants uses x PPM of ammonia doesn't mean there's enough bacteria in the tank to process that x PPM of ammonia.
The OP is not using the Walstad method. No one mentioned using mineralized soil. The OP merely asked questions about how to do a fishless cycle using ammonia.