The biggest mistake of all youtubers making videos of their metal detectors' performance in target separation is running various nails+coin combinations in Air Tests! Unfortunately these youtubers don't understand that the Air Tests have nothing in common with what actually happens in the ground with different types and concentrations of ground minerals. Not to mention Halo effects of ferrous targets! If you do the same 2 nails + coin setup as in your air test but at a depth of 4-5 inches for the coin in the ground, even without the halo effect, you will not hear the coin. And if you set the 'dt' to 6, you will only hear a high tone response, even if you remove the coin. Never use the misleading Air Tests to display your detector capabilities!
You are correct in an "Air Test" not being the same as an in ground target. No matter what, the Ground sets the rules in real life detecting. What I show on the unmasking portion is meant to be a visible example of typical 3D in ground targets. It is a learning tool. It is for showing the detectors behavior, not it's capabilities. I try to mention this each time but do not record from a script. There is nothing misleading if a viewer has anything more than basic experience or they have simply watched some of my other videos. Not shown in any of my videos is a buried, 6" deep Copper Cent with 3 nails positioned "Monte Berry" style above it. All at different depths. It is not an easy set up. The Legend hits the coin better than most, and dt does help some. Not much, but it might be just enough extra in the field. The drawback to the dt feature is that it does distort the audio response at higher levels. Personally, I see it most helpful working in mineralized soil.