Dah-veed, I think the issue is more that by following the representation on Apple's website, customers could do a one-way upgrade to iOS 5 and *lose* functionality they'd enjoyed for several months. I don't think any legal action would hold up as the multitasking gestures had been enabled for development purposes via Xcode, but I think it's a little insensitive to be dismissive of these concerns, too. If it had been disclosed at the time of the upgrade that it would result in multitasking gestures being disabled on first generation iPads, many people might have opted to skip upgrading.
Certainly mistakes happen, and they're generally covered by disclaimers. It may be that Apple erred in not specifying "iPad 2" on its website or the upgrade notes, or it may be that the omission of the gestures on first generation iPads was a mistake. Either way, it'd be nice for Apple to own up to it and provide an explanation.