The point is that people seem to think that it’s impossible to live past 120. And there have not been ANY men (as far as I know) who are recorded to have lived past 120, whereas there are women. Even if there was only one such woman, the point still holds true – that we see that a woman can live past 120, and we don’t know that a man can.
And if this is all based on Moshe Rabeinu, it makes sense, since he was a man, and since women do live longer than men on average.