Well, I have doubts about the claim that flushing draws out metals and toxins... How? Heavy metals are immobile. Flushing can remove elements from the root zone, but I don't believe the plant actually expels anything during the process. Otherwise, outdoor plants would suffer from deficiencies after a heavy rain.
The wiki on EDTA mentions that it is a "Persistent Organic Pollutant" - That may be an important consideration those who are more environmentally inclined.
Final Phase may contain citric acid, but isn't "mostly", citric acid. If it was, the MSDS would have to reflect that. It's likely a very small concentration. Fact is, it's mostly water.
I'm really starting to think this is pretty well just sugar-water and Epsom salt with lemon juice. Not that there is anything wrong with that, per se. It's just that at +$50 a jug, it's a little pricey. I could make that for next to nothing. Hell, I could mix it up with some lime.