This whole discussion is flawed. If your PH is 7.2 there is NOT nothing in your water. I take it you are using tap water? Majority of which would be calcium, magnesium, phosphates and sulfates. Also some nitrates and others like iron etc. Distilled water with 0ppm is about a PH of 6 and Its also very unstable. Flushing is a poor term to use in hydroponics since it only really applies to soil in my opinion. They are trying to rid the soil of salt buildup and excess nutrients but there is still nutrients that remain. In hydro my opinion is we should just lower our ppm as we get later into flower and keep on top of salt buildup throughout the grow with proper water changes. I think this is why most see an issue with K in flower as Na will affect K uptake.
If you are looking to get better tasting weed your efforts are better spent drying and curing properly in my opinion.