Have you personally actually used pond shield, and/or talked with Butch?
Do you speak from personal experience?
I have personally used pond shield. Had trouble at 1st, due to not following the instructions correctly. Even though it was my own fault, Butch cheerfully next day-ed more pond shield at his cost to replace what I had screwed up.
The way I see it, if done correctly, for what it was designed for, the only reason it's not going to work is because the person applying it didn't follow the directions. Plane and simple.
Pond shield is no different from any other sealer, what ever you use, it has to be applied correctly.