I think you are suggesting that if the cell output temperature is constant after boil off, the heat flow from the cell is constant but that is clearly incorrect.
Nope. I did not say that, and neither do the papers from F&P. I suggest you read them more carefully.
To reiterate, in a blank cell, the temperature begins falling immediately after the power is cut off, following Newton's law of cooling. In a cell undergoing heat after death, the temperature rises, and stays high. It does not fall. This is first principle proof of energy production. The question is, how much power does a given temperature indicate? Determining that is somewhat involved, as you see in the papers.