Considering the structure of a MOS transistor, it is symmeteric, ie, the Drain and Source terminals can be interchanged. For a PMOS transistor, the source is at a higher potential than the drain and, for NMOS the drain is at a higher potential than the source ( the source is always at the lowest porential in the circuit).
Keeping this in mind and now looking at the configuration I had mentioned earlier, the drain and source of the PMOS and NMOS can be interchanged. So, now the transistors should be baised properly at some point and therefore should work as a kind of buffer.
Correct me if I'm wrong!