I think Snipe nailed it when he said soil issues and adapting to their peculiarities should be addressed in the construction. Nothing beats a liner constructed from clay with good plastic properties. He is able to transform his troublesome loams with soda ash into an acceptable clayish liner with acceptable plastic properties. The filtrations results of his cores do tell us that it doesn't take 100% clay to have a good pond bottom.
I don't know what Soil Floc is made from but I think it likely that its polymer is polyacrylamide or what is widely called PAM. I have no doubt it will work and I think it works for similar reasons that bentonite works. It forms an layer of low permeability at the interface of permeable soil/strata. I see a much greater benefit with a polymer when there is things like rock seams taking water. Bentonite is very dispersive and it will tend to stay dispersed in pond water, which is why I suggested it may work better if precipitated with a flocculant. In the end, if there is filtration, the bentonite or the polymer will be drawn to it and they will bridge the interstitial spaces near the boundary. I think a polymer works better when these spaces are large (eg rock seams, vugs, and fractures). A blowout? Its probably better to reconstruct IMHO.
I think Bentonite should only be used when the soil is primarily chemically inert components (e.g. primarily sand). It should not be used where the soil chemistry is coagulating clays already in the soil. The tendency will be to do the same thing to the bentonite reducing its performance.
Snipe's method of constructing a liner treated with dispersant is appropriate for these soils.
