This is unfair, in my view.
It was the performance in the King George (when he stopped as if shot, between the last two) that raised questions about his stamina. Until then, the prevailing mindset had been that it might not matter that the Betfair was run over shorter than advertised. It was only after the King George that people questioned the real merit of the Betfair, when it came to his stamina - a position that - far from being childish - was, and continues to be, entirely justified, given Cue Card has done very little since, to dispel the questions about how well he stays in top company.
Don't forget that the first two were massively favoured by the weights in there Charlie Hall, and the race barely presented a stamina test anyway, as Cue Card was given an easy lead and allowed to dictate. In a better race (like a King George) he would have the gun put to his head again.