They say the binding site adds the increased energy. Supposedly, the binding site picks up kinetic energy from the rotating wheel. It then creates a force which increases the energy state of the electrons which bind ADP to Pi. Here's the physics of the subject. An osmotic gradient is a source of kinetic energy.
Kinetic energy means a mass moves.
Protons are mass which move across the osmotic gradient. A truism is that kinetic energy cannot be transformed into chemical energy, because force or motion of nuclei cannot be converted to force or motion of electrons which orbit nuclei. Chemical energy is in electrons which orbit nuclei. It always moves down hill in chemical reactions except where radiant energy is added through photosynthesis. Electrons orbit nuclei at approximately the speed of light.