I can see that you haven't dueled a decent polearmer yet who can make use of the polestun.
The only way someone can get a "free hit" in a duel using polestun is by using a fast, non-knockdown pole (Spear, for instance), hitting you in the head, and hoping that it triggers the full 1s stagger animation.
See Walt's post on WPF affect on swing speed. Only non-knockdown weapon data points below 1s could possibly allow a free hit, which is basically Spear >140 WPF.
http://forum.c-rpg.net/index.php/topic,2531.0.htmlAnd even then, it's a 50% chance, and only on blows to the head. Torso is 50% chance for 0.8s stagger i believe, at least this is what Paul hinted.
In a realistic scenario, the guy probably has a MW Bec and is wearing armor, for a swing speed in the 1.075s range. MAYBE with turning into the swing+lag, he could get a free-hit on the stagger, but again, only on a blow to the head. If you are letting someone smack you in the head with a Bec during a duel, you're going to lose regardless.