The question of whether machines or humans are stronger is moot, isn't it?

In any intellectual contest between human and machine, all the machine winning implies is that the endeavor is algorithmic.

The machine can be given practically unlimited memory and compute; we consider it cheating if the human would use memory aids. The machine could be implemented as many agents cooperating; we'd think it's not right if thousands of humans collaborated to face the machine, etc.

So statements like "not a sign that humans are now stronger than AIs at Go" are pretty meaningless, IMO