For the moment I choose to believe that all this is just a smoke screen. I believe, and this optimism is in part due to the fact that I have now had coffee, the Doctor (if the report is right) is merely glossing over complicated stuff when asked a difficult question by a kid in a tense situation. We know he is lying, as we know more of the back story than this Clyde character. And he is of course right. It is technically possible, I think, to revive someone from the Matrix thingamajig and give them a new set of regenerations. I have a sneaking suspicion that that has been done for Rassilon in the New Series. And so you could technically argue that the Doctor is telling the truth.