On Einstein's equivalence principles

EEP has something more than what WEP has. WEP states that in a small reign of space-time,there is no difference for a particle to free fall (to move in a gravitational field) or to move in a box with acceleration $g$ in the inverse direction.

Then Einstein stated more and said that not only for free fall but also for any non-gravitational experiment, this equivalence exists.

For example, we consider an electron and a proton.They fall with the same acceleration in the gravitational field and independent of their mass.If we then combine them and make an atom,the free fall acceleration of that atom would be the same.We know that the mass of atom is less than the total mass of electron and proton and negative potential is added to the system. Here we see that in addition to mass,gravitation is also coupled with energy.