Glucose gets broken down into pyruvate via glycolysis, which is by far the primary way in which you generate pyruvate. This process generates a bit of energy, but the vast majority of ATP is generated during the Krebs cycle, which is where glucose metabolites (namely, pyruvate) get oxidized into CO2 and H20.
To respond more directly to your point: if 80% of glucose is immediately metabolized to CO2 and H20 (I don't recall but I'll take your word), that means that 80% of glucose enters the body, undergoes glycolysis, and then enters the TCA cycle. This means that 80% of the glucose in your body is quickly converted into fructose (yes, F6P). You could easily make this into a pure fructose molecule with a phosphatase (though this doesn't happen in vivo). The upside is that phosphorylated sugars cannot be transported by facilitated diffusion, so F6P will remain intracellular.
I'd also like to point out I'm not drinking a shitload of this stuff all at once. The reason I avoid this is to avoid an insulin spike, which would, without question, defeat the purpose of using dextrose.