no bro flush is not a myth at all ..
if you feed light and right you can get away without flushing and it will taste great but there will always be some traces of pk ...
let me tell you how it must be done
you want your plant to stay green all the grow, never yellowing ( i used to fade the plant during my flush its a big mistake). if you yellow it in fact, by wanting erase the nitrogen to not have that horrible chlorophyl taste we all tasted one day and that traumatized us, you will also kill all the future sugar that will give your bud that great taste ..
that green and not good tasting chloro will transform into sugar during your drying, thats why it must dry 10 days minimum in the dark, so the chemistry happen
you want to flush the excess salts of you medium without starving the plant
in hydro it can be very fast ... like 1 week if you have a small medium
and thats considering the week before that flushign you slowly decreased you nutrients level
real science right here took me some years to notice
tell me what u think