I think what he might mean about flexibility is to do with going forward. Adding a feature to a piece of code can easily add cruft. Refactoring removes the cruft, replacing it with a more flexible piece of code that, whilst not intended to add functionality, gives room to more easily add functionality at a later time. Which might be 10 minutes hence, but still, that's still a later step.

I've tried to do XP before; it's hard and tiring. Oh, you can get a lot done, true, but you have to work at it. And you have to work at staying in the process. The most obviously difficult part is matching suitable programmers for pair programming.

Wade.