I just saw this technique on You Tube, and although the guy was really selling it, and his demonstration looked really dynamic, the technique is fundamentally flawed. I also see this technique employed as a block, raising the stick over the head to block a vertical strike or thrust downward to block a kick.
One tendency of this technique, holding the stick in staff grip, palms down, is that you’re "on the tracks," meaning that this tends to place you head-on to the opponent. Used as a block, there are so many counters to this technique (a subject for another video).
The real problem with the upward bar strike to the chin, though, is that you must be really precise to hit with it. You’re aiming to come up under the opponent’s chin, but if the strike is too short, you miss completely. The trick is to get close enough to his upper torso to hit his chin, but not so close that your stick gets caught on his chest or arms as it comes up. He doesn’t even have to try to grab your stick for it to become entangled with his hand or arm.
Simply by changing grip to rifle grip–right hand palm-down at the butt of the stick and the left hand palm-up maybe 2/3 of the way up the stick, you can hit easily, counter a grab, and move to the opponent’s outside.