Bacterial establishment has everything to do with testing. Since - its bacterial establishment that results in ammonia and nitrite falling, nitrate rising and subsequently falling. Testing itself does not alter the process - or at least it doesn't need to - but many protocols exist whereby you add x amount of ammonia to lets say 2-4 ppm, and then test - once it reaches 0 or near 0, you add the same amount of ammonia and see if indeed it is processed. This isn't my protocol, and I'm not defending or criticizing it, however, in many cycling protocols testing is part of the process. So - anyone making a blanket statement about testing IMHO is sending a message which may be misunderstood by (especially newer) reefers.
You happen to like a method closer to what
@Lasse recommends - and what I do myself. When starting a tank, I add dry rock, bacteria, and a very small bioload. I have never used an ammonia test except with various experiments I've done and posted on the site here. In fact I just moved 10 or so adult discus from one tank to another 210 to a 72 gallon temporarily - I added bacteria and the fish - which are doing fine. I do not plan on testing ammonia.
You said: 'Crash usually means a loss in bacteria to keep simple. Unless you add something that will kill all the bacteria. It won't crash. Any ammonia seen will be depleted by bacteria as they further populate" - IMHO, A crash is when multiple animals (vertebrates and invertebrates) die off quickly - this can be one fish that dies of something, decomposes, and there is a nutrient spike causing more problems. The aquarist keeps feeding hoping to turn things around - and it gets worse. A Crash is usually due to a toxin (such as an environmental issue or low O2 or potentially ammonia)
You said: "Testing is a great way to show things are off but not determine if a tank is truly "cycled" nor determine the amount of bacteria".
Again it depends on your protocol. But - there are clear definitions of how to tell if a tank is cycled using testing. Because you and I don't necessarily do that testing doesn't mean it's incorrect or unnecessary to do testing. And- yes you could tell if your tank is cycled by adding ammonia and watching it decline - of course, one would not do this with an established tank - this is just an example.