Well, my personal objections to the idea of chivalry aside, it's probably your real-world answer. Trek's odd like that - it insists that women be capable security guards, soldiers, etc, but then also has difficulty treating them like they are.
More on topic, do we even know if in-universe it's intended to be a Vulcan pinch? Surely other cultures have developed pressure-point attacks or the like that cause temporary unconsciousness?
right, though, in that we don't really need to know how and when he learnt it (whatever it was); it makes sense he would, so it's not really a "hold on a minute..." moment.