Hah, I noticed the same thing writing fiction with fable. Most models seem to go into a sort of "storytelling mode" where they forget their PhD level smarts. I had a character who is doing repair on a satellite. Most models would give you a half-baked explanation with some technical terms - half of them right half of them wrong.

Fable gave a description so deep that even I couldn't figure out what was going on and had to ask it to give me a simpler explanation.