Its a lame excuse because if you don't want your battery to take a hit, don't go to a flash-heavy site. A properly written mobile version of flash shouldn't use any resources if you aren't decoding a flash site. We're smart enough to not use Youtube when we don't want to drain our battery; we're smart enough to manage flash usage as well.
I'm hoping it was left out in anticipation of the redesigned Flash Mobile and Apple is waiting until the SDK is out to encourage us to upgrade by offering it only in that firmware update.