Yep, you're almost to the point where it starts to explain the "slow in, fast out" approach. Keep reading and you'll see you want to maximize your exit speed (as the title to that section indicates) so you can carry more speed longer. This in turn gives a "sharper" turn in angle to make the exit a "longer" straight away, so you can get more acceleration out of the vehicle, that will ultimately give you more speed.

I read that book many, many years ago (as well as several others). Good book.

Hmm, doesn't go against my natural instincts. Perhaps you should try a more open track where walls aren't a factor. Too bad you're not near Michigan, quite a few around here. Of course, there's always a wall somewhere, and my one buddy always seems to find it.