My thought (in chem nutes) flush is needed. I get a nice white ash that burns all the way down.
The theory for me on the yellowing is that our plants are an annual flower. They bud, get preggo, drop
seeds and die. I want the plant to use all of it's reserves everything. Before finally getting chopped and coming down. I have seen hundreds of arguments, blah, blah, whatever. This is a personal thing that I am trying.
My ideal bowl = Lit once, continues to burn evenly and smoothly... Continues to burn into a light white ash.
I have smoked so many bowls that come no where near this. Black char, harsh burn, especially from clubs.
With organics it is a whole nother conversation and many more arguments, lol. Don't flush, Do flush, No Ph, Always Ph, etc. Just my little experiment chasing the perfect bowl.
Rather or not it will increase the amount of THC is another story. I am not a scientist nor do I posses the equipment needed to know if there is any difference. Like I said my main concern is the smoke. Also I don't think there would be a big enough difference to say one way was better than the other.