They're one of the best methods to using an entire grow space and maintaining an even canopy, in my opinion. Scrogging is a method of LST, it's just the net is the one keeping everything "down" instead of plant ties / string etc. I scrog exclusively since it gets me the best yields. I'm not sure...
The color of burning ash is also one of the ongoing stoner myths. And the test your friend performed is not what I would call a reliable scientific test in the least.
Gotcha, this is true. But it's those that disregard the science because they swear they can "taste" the difference, so they say you have to flush. I've had someone here previously tell me she can taste the magnesium if she doesn't flush. lol
It's been proven by SCIENCE harvest flushing for the reason people flush is wrong. So if you think one persons olfactory can pick up "nutes" in a bud vs a scientific experiment using tools that can actually MEASURE these values is somewhat...interesting.
It is, and always was, about the cure.