about white ash ... not a myth at all
if you think cigarettes produce a white ash then you never smoked white ash bud.. it's grey at best.
flushed buds do not produce white ash , its the contrary (used to think this as well in the past)
i invite you to inquire about white ash in cigars ..
an exemple
"The color of the ash essentially indicates what minerals are in the tobacco. Basically, if the ash is white (or gray-ish), the likelihood is that the tobacco was grown in very rich, nutrient-dense soil. A darker – or black – ash, indicates less mineral-rich soil. Mineral content does affect the flavor of the cigar. A general rule of thumb is that fewer minerals in the soil will produce a more acidic flavor in the cigar. That’s not particularly pleasant to taste or smell.
To be a little more precise, a bright, white ash shows that the tobacco has received enough magnesium and calcium from the soil. Cameroon tobacco, for example, used mainly as wrapper leaf, tends to burn with a bright white ash. If your white ash is flaky, that indicates too much magnesium in the soil. Cuban tobacco produces a grayer ash."
From experience, I can tell the healthiest plants are the harvest produce the best quality, and also the whitest/thinnest ash possible.
In contrary flushed, faded plants usually produce the lowest quality, and a grey ash.
In worst cases a black ash will be produced, which is no good.
About spending the last days in the dark it has a benefit, among other things.
I use flock rockwool for years and i always let the plants close to wilt before harvest.
Then i turn off the light and let the plants finish to die on the vine a day or two, in the dark.
When they are all done, they go in the dry room, and at this moment i can take off the trunk piece remaining in the pot, and reuse the mapito, it's totally dry
I have the same mapito for years. It's also doable with coco IMO