1 It doesn't have to be- you can take it part-time. If you do it full-time, it has to be intensive because there's a lot to get through in the time. Would you want to study with a teacher who'd done an easy course but didn't know much?
2 You only do a few observed lessons, so the more time you put into them, the more you will gain from them. Teachers don't put in anything like the same amount of time when working, but the first lessons are the foundations, so it's worth doing them well. Would you want to be taught by someone who thought that 30 minutes' preparation in training was enough for them to grasp the basics?