I'm answering both you and the previous one in the chain. I used huggingface's OpenAI detector[0], the pizza example is detected as fake with 99.98% probability, whereas the Battle of Agincourt text is also reported as fake with over 99% probability. I don't have any example at hand of how much "real" text on these topics to try and see what that model detects, but up to this point[1] this text is reported as 99% real. You can play and see how much % it assigns to different examples.[2]

[0] https://huggingface.co/openai-detector

[1] I had to cut somewhere to copy and paste into the detector, so [1] is the cutting point

[2] My whole response was still detected as 99.98% real, and copy-pasting the Agincourt bit at the end still reported as 99.98% real. However, moving it to the start (having my answer as a last paragraph) made it detect as 97.71% real. Deleting only "huggingface's" balanced it as 54% real. You can play around with the demo to test different variations of any text you analyze with it.