For someone who says others are unable to follow a conversation, you certainly show yourself to be unable to do so.
You are talking about stability during a discharge cycle. Of course that is important, and nobody is saying anything that even remotely contradicts that. This is the 'stable voltage range' he is refering to.
But he was aked about the FAILURE mode of the batteries. And in answer to that he said there is a narrow WINDOW which will produce that stable voltage range. The WINDOW is refering to the CHARGE voltages that are required in order for the battery to produce that stable range on discharge. There is only a narrow window of charge voltages which will produce the desired output.
By reading ALL of his answers, you can see that the problem is that, on every cycle, more of a film builds up on the anode. This film interferes with the charging process (ie. less voltage is reaching the electrolyte). As long as the voltage is still in that window, stable output results. After a certain number of cycles there is enough film that the voltage reaching the electrolyte is OUTSIDE that window, and now the battery can no longer produce that stable voltage. The cell has FAILED.
And the solution he provides to the problem is to prevent the build-up of film by plating the anode, which can't be done with the liquid electrolytes. He is in no way saying the problem is the stable voltage range, he is saying that in order to keep the DESIRABLE stable voltage range, you must stay in the window by preventing the film on the anode.