The villain is stronger, and is defeated through some combination of circumstances and advantages that allow the hero to bypass that strength or temporarily exceed it (typically through significant effort and/or sacrifice, often prior to the confrontation).

Right, that's what happened in this story: Harry temporarily got the upper hand on Voldemort. Voldemort allowed Harry to get the upper hand. When Voldemort possessed Quirrell's body, he didn't just take over the world over the course of a week. When Voldemort realized that Harry was an existential threat, he didn't relieve Harry of his limbs, mind, and freedom to move outside a little box. Voldemort allowed Harry to be a threat because otherwise there wouldn't have been a story.