Yet many on here claim can play 9, easily, within 15min. Sometimes I get the feeling there are more bots on here than humans.
You have to realize that these players you speak of, the ones that can play a 9 Hole round in the 15-20 minute range, have been playing this game for years. Over and over again. Round after round. They have seen and experienced every possible scenario.
With that being said, they know ( from their experience ) how to play every possible shot on every possible hole under any given situation. It has become second nature to these types of players. They do not really have to think about the shot any more.