The half seat or 2 points position as you called it, is great for long distance, and for super uncomfortable horses. trust me if you want a comfortable canter: stay away from jumping horses. It's also great for speed when you go from one jump to the other just remember to sit the turn to help stability, and before the jump to feel the rhythm and set the take-off point. Sometimes you also need to use it for horses who are very sensitive on their backs, so if you have a horse that hates a heavy seat and bucks when you canter them, a half seat is ideal. You can also use it to ask your horse to stretch themselves the canter and let them get their own rhythm without having to follow your seat.