I think common sense and Apple's pattern of product development is more compelling than a lack of proof. None of Apple's products went from concept to market in the rapid timeframe you're accepting. Considering that Apple is super secretive about its explorations, they are not going to announce to competitors their research by filing for patents before a concept has been studied.
You can credit Cook for fulfilling the watch's delivery. I doubt he deserves credit for its gamble; otherwise, someone within Apple would have publicly credited him for the decision as they often did for Jobs.
Cook is a manager. I doubt he is a gambler—at least not a risk taker. Nothing unexpected or future-defining has materialized during his tenure. Airpods? A natural evolution. Homepod? Apple had a hifi speaker during the iPod era, and the current one is a Me Too product with unexceptionable abilities. Wireless charging pad? Odd that its development was acknowledged and that it was an admitted Unicorn. Apple car? Apple VR? I'll wager that we'll see another CEO at the helm when those concepts become products. Who will you credit if that happens?
Cook has no reason to care if he's not personally recognized for Apple's continued innovations. Yet it's important to the Johnny-come-latelys who embraced Apple's brand in the post-iPod period. Cook is their brand priest. As much as they don't identify with the Jobs era, they want to believe Cook is Jobs 2.0.
You said it yourself, Apple is super secretive. That means any guess about how long it takes to get a product out the door is a guess. Not even an educated guess. So watch, homepods , AirPods design could have been started post 2011.
I’m sure Steve and tim discussed accessories and these types of things came up. The question is when did actual design start.
Yes, I believe Cook will have a successor and who will you credit when the successor gets products out the door(even ones that aren’t revolutionary or earth shattering). Steve Jobs? Many people are stuck like a broken record at the Steve Jobs era, yet it’s probably not the core of hardcore Apple fans that catapulted Apple towards trillion dollars. And it seems for some it’s important for the so-called core fans to discredit cook as much as possible, in the new post-Jobs Apple era. Cook is the captain that is seemingly taking Apple where jobs couldn’t.
Cook isnt Jobs 2 and maybe that’s a positive but he combines the best of Jobs and the best of Cook and Apple is better off for it.
And by the way what did jobs do, invent a new cell phone that was popular? And a new form factor tablet, where tablets already existed? And yes I agree the tablet was popular.