I dont think anyone is saying adding live rock to a tank with high ammonia would bring it down within 15 minutes, very few tanks (especially ones you would be pulling live rock from, as you typically want the most mature rock possible) maintain a "detectable" level of ammonia.Just curious, what foods are you recommending - you're recommending low protein foods (a major ammonia source)?
There is a time to test and there is always a time to test but not needed.?
I look at cycling testing for a novice aquarist and anyone else who wants to do it as a large advantage over not doing so - this is because one can actually see what's happening in their tank (when just starting up - ammonia, etc levels are certainly going to be unstable). I've already admitted that I don't use ammonia testing - or dosed ammonia (except in my experiments posted here). But - the way I learned to set up tanks was either with mostly live rock - or if using dry - at least 'some' dry rock. You can look at those in the experiment section. BUT - they do contradict the comments that a given chunk of live rock can immediately assimilate ammonia to non-toxic within 15 minutes (This is not in my experience true) - and they also contradict that idea that additional (the number) of ammonia reducers do not increase with more 'food' immediately or even within a day.
As such it would make sense that unless you are going overkill on the live rock, there would not be enough ammonia consuming bacteria to handle a sudden shift to .5ppm ammonia as the bacteria on the rock grew to support a system with a steady influx, but relatively low availability of ammonia and would have to be given time to multiply and tackle the much higher ammonia