Personally, I can't think of a reason why you'd rather swipe back to a page that could potentially be out of date.
EDIT: In any case, although it appears to go through the motions, I don't think it actually does.
EDIT 2: It doesn't.
Sounds like what the iPad does then, the blue bar starts to fill as you go back?
Then if it's been an hour of so, when you go back it will actually reload it properly? The iPad uses it to mask the lack of ram I think.
The reason I like going back sometimes, is when you've bought something, then realise you want to go back to the receipt or summary on the previous page, if it doesn't reload you get what you want, I'd it does then you've lost it as the session has ended. Or if the transaction fails on the next screen, you can go back and try again, if it has to reload, again, you can lose what you have done up until that point.