The doctor recalled that the pilot, when asked if he felt unwell before the crash, replied “yes”. The investigation could not establish if the
pilot understood the intent of this exchange, in what way he might have felt
unwell, or if this was his answer.
If the doctor had asked him "Are you a hippopotamus?" he might have given the same reply. Presumably they had to put this in the report for the sake of completeness, but the report makes it clear there is nothing to be learnt from the reply "yes".