A statistical or ensemble description for the outside fixed position observers becomes necessary if they give up information about the initial state of the collapsing stars, believing that the collapse will lead to a final geometry with a fully realized horizon. The ergodicity of the inside co-moving observers' oscillations around the system's center becomes unavoidable due to the complexity of interactions between different parts of the collapsing star. The initial state ensemble of the outside fixed position observers and the ergodic oscillations of the inside co-moving observers form a quantitative complementarity for the microscopic state of physical black holes. References and demonstrate that quantizing either of these two descriptions yields the correct area law formulas for the Bekenstein-Hawking entropy.