HBG do not turn into GSF. HBG do have a place in pond management, certain circumstances they are excellent, many circumstances BG are far better. Bass readily eat GSF, they are more fusiform than BG. However, because they only spawn once a year while BG, especially in southern areas can spawn 4 times a year, means BG produce more forage for the bass to eat.
Many of what is written on-line is put out by fish and game agencies who are advising people on main stream common management practices. Generally this means the LMB/BG/CC stocking regime with perhaps RES thrown in. We all know there are other options out there for stocking ponds, with the proper management and goals of course.