Haha - I am on session nine this week too! I've been moving through the program rather slowly - but I don't ever want to move on to a new session until I feel I have really worked hard and done everything I was supposed to for the last one. Anyways - I think I see why this is supposed to be good for us. This is all conjecture, though - I don't profess to actually know what I'm talking about!! Haha.
For one thing, I think it teaches us that the physical sensations are not necessarily coming from any underlying ailment (b/c we can create them on command by doing simple, non-dangerous things) - and, more importantly, that they are not going to kill us (b/c who ever died from breathing through a straw for a few seconds?!). If we know that we can turn these types of feelings on and off, they will hopefully become less scary.
Plus - it's exposure. Exposure to those terrifying physical sensations. In my experiences with exposure so far over these past few months, the general pattern is that at first it causes an increase in fear (b/c intentionally going into scary situations is way more frightening than avoiding or quickly escaping them), but then through repetition that fear drops big time. So if I can get to the point where hyperventillation and dizziness no longer scare me, for example - then next time I'm driving and I start to get those physical sensations, it won't be a big deal.... Hopefully. Like I said - I have no idea whether I'm right on any of this stuff - but I'm going to try it and find out!