It can have an impact, but beyond the physical impact, it can have an effect on the pitches themselves (e.g. the sinker doesn't sink the way it normally does.)
Yep. So why not give Stammen and Zimmermann a couple of extra days in the mile high city. Even if I an wrong, I'm right because it can't hurt them to get used to the altitude. Maybe I just see it as a no brainer.