I think you're labouring under a misconception about code review in particular and XP in general. It isn't the case that all code's written this way, or that the 'guru' writes all the code. It's people who happen to be working on the same project sometimes collaborating to write new code, or perhaps to look at code they've already written. Either person can write code and either can comment. It's categorically
not a case of one person programming and the other spectating. In my experience this works well if applied sensibly rather than dogmatically and it's actually quite close to the way I've tended to work in the twenty or so years I've been developing software.
Also the "Extreme" in XP is, I think, quite misleading. While I'm as keen as anyone on a bit of extremity XP actually tends to make things less "extreme" in the sense that software developers would normally recognise (i.e. extreme == 16 hour days, crazy deadlines).
