I can not see what flushing actually does to a plant or its root zone that would translate into a better 'taste'. Like HomeB said, if the goal is to leach salts, water is the way to go. Maybe the Final Phase, with its Chelated magnesium and Sulphur? I think not. Did advance discover a new amazing reverse-chelating agent? It's all bunk sir IMO. And for the record, I have tried Clearex and FloraKleen and noted no difference. What one should do is merely decrease the PPM's of your feeding close to harvest or just feed ph'ed water only.
If you read the Advanced narrative on Final Phase you will note they really just contradict themselves and finally mention their "proprietary" mix, as usual. Whatever the product is that bucks common chemical or botanical sense they will say "proprietary formula" . Buyer beware.
Advanced take on Final Phase