He ate the fruit and told us that he felt the effects were positive.if he didnt care about the basket thing, why would he care about how he was told he "felt"
wait do you get told how you feel?
The narrative is important. If Tim and I have been handed fruit and we get the opportunity to eat it tonight (that's if I'm not lynched), we can confirm Ender's story.
If anyone else gets abducted and the narrative is different to Ender's we can tell that;
a) Ender was possibly lying
b) There's been a shift or change or;
c) An action took place