[Ibby]

Godspeed You! Black Emperor, for example, is vastly different from say, The White Stripes. Even if you say GY!BE is rock, it's still post-rock, because it's certainly not the same thing as other types of rock. You can't claim there's no such thing as grunge, because 'grunge is still rock', any more than you can claim that post-rock isn't post-rock.

Post-Punk has nothing to do with Post-Rock. Post-Punk was a snappy thing to call stuff when new-wave wasn't snappy enough, or whatever.
Post-Rock sounds, feels, plays, and down to its very core is different from a LOT of what's out there. It is very definitely its own style, whether or not that style is still part of 'rock' as a whole.