In the long term, the only thing that _can_ increase wages on average and in general is productivity. Productivity increases mean the pie is bigger, and without that, there is no where for increased wages to come _from_. So by saying that producity only results in increased wages in the case of the worker uprising, that is equivalent to saying that wages can only rise from a worker uprising. The only way this isn't true is for some other proposed mechanism for worker wages to go up, and the only other methods would be short time, single increases where all you are doing is taking from someone else (presumably capital I guess?)

Sustained rates of increase _require_ increasing productivity. So no, they didn't explicitly state it, what they explicitly said was that productivity only results in increased wages if a worker uprising forces it. But that's the logical requirement of that statement.