I don't assert that there are many blind people who would be unhappy if they gained the ability to see. Possibly there are none at all.

If blind people and sighted people are equally happy (albeit for different reasons), I suppose DanielLC's comment can still be true, so fair enough: you're right. My conclusion doesn't strictly follow, I was making inferences about their model. (I suspect they were true inferences, but I was still overconfident.)