Hard to tell from the pic in the article because it is black and white, but I highly doubt that fish is a pure BG. I am betting it is a BG/RES hybrid.
If you were looking for "ponds where don't want fish" with the potential to grow monster trophy hybrids, there will be some reproduction from the hybrids. You would need some type of predator to eat their offspring. If you stock LMB, you'd have them reproducing... Perhaps you can consider stocking a small number of HSB every couple of years. Say 30 every other year. If you don't feed them, they should stay hungry and heavily prey upon the few offspring your hybrid sunfish produce. This is not normal stocking practice and I am not sure it would be perfect, but HSB will not reproduce in a 3 acre pond, so they would be easily managed. It wouldn't be a pond without any fish, but for 3 acres there sure wouldn't be many...
