I think it's interesting that Steve Jobs has earned this much credit with most of us (I think most). He has a history of saying stuff that is either clearly true at the time or turns out to have been surprisingly frank in hindsight.
My guess is he was shooting from the hip and then discovered that it was a much bigger pain in the ass than he realized.
The right thing to do when you make a promise without fully thinking it through is to still follow through with it, no matter how big of a pain in the ass it turns out to be. This is how people (should) learn to keep their mouth shut and stop over promising and under delivering. Jobs is not one to over promise so this instance is interesting.
My guess is he was shooting from the hip and then discovered that it was a much bigger pain in the ass than he realized.