I’ve read this a few times and I’m genuinely not sure I understand what you’re saying.
4/6th is a smaller ratio than 5/6 the only way for 4/6 to be greater would be for the area to increase.
Expressed as percentages it would be 66% (approx) eaten vs 83% (approx) where the person that ate 66% ate more pizza. The only way that’s possible is if the area of the pizza that 66% of was consumed was greater. (Strictly speaking the volume could be at play here too but I’m going to assume they’re the same height for the question).
I genuinely don’t see any way his thinking was wrong, or how this could be answered another way.
I might genuinely be missing something but if so this question is poorly worded.
While a fair idea there are two issues with that even still - Hallucinations and the cost of running the models.
Unfortunately, it take significant compute resources to perform even simple responses, and these responses can be totally made up, but still made to look completely real. It's gotten much better sure, but blindly trusting these things (Which many people do) can have serious consequences.