I find it more interesting that he said they worked on the Watch after Steve's passing (Oct 2001), but in the keynote he says they were working on it for 4 years, which would be started before his passing.
You think he and others hid this project behind his back? Or is he trying to steer credit away from Jobs and to himself?
Apple prototypes everything. It's very likely that the iWatch was in a very early concept planning/prototyping stage in 2011. However, that doesn't mean Steve Jobs had green lighted it to become a product or even knew of its potential.
Kevin Lynch, according to Cook, led Watch OS development. He wasn't hired until early 2013. Apple ramped up iWatch development in the last two years.
Cook talked a little bit about the period after Jobs death in one of his All Things D interviews. He essentially said they finally had to move on.
But what happened to Steve leaving Apple with a four year product pipeline?
Things change. Jobs couldn't have predicted what Apple would need to do. At least two of Jobs's final projects haven't even seen the light of day yet (Campus 2 and the forthcoming Apple television). iCloud was one Jobs's final projects also, but Apple seems to have rebooted it somewhat (with iOS 8's iCloud drive).