No, this is a rather confusing point. Students often look at this expression and thing that the standard reaction free energy in this expression refers to equilibrium. It does not. The standard reaction free energy is simply the reaction free energy when the system is in the standard state (all solutes 1 molal for a solution). Generally, that is not the equilibrium condition. So what does this expression mean? It is simple a consequence of the way we define the standard state and the equilibrium condition. Because the reaction free energy must be zero at equilibrium, the standard reaction free energy must be balanced by the RTlnK term.