What is combinational circuit?
For me a short-circuit isn't combinatorial nor sequential. It's an error, it may fry the circuits.

The circuit, regarded as a black box, is still in scope of the combinational logic definition: its output values depend only on the current values of the inputs;

You can make a logic inverter with high power relays. You set opposite tensions, the relays or the wires connecting them turn into melted metal. You have a memorised effect (blown circuit) : It is sequential!