I think they are being overly kind. The conclusion itself shouldn’t be sensitive to just removing the all H if all T answers. Since their trend disappears from

I think they are being overly kind. The conclusion itself shouldn’t be sensitive to just removing the all H if all T answers. Since their trend disappears from removing just those answers, were only left with the far more mundane “older people are more likely to write all Hs or Ts”. The true conclusion was hidden by the averaging that goes on when you make a best fit line.