AI generated text has no human centered underlying model of physical reality and its metaphors are tortured as a result.
If we had talking centipedes the results would probably be similar, but for different reasons.
That, and one can feel that there is no intention behind the text. There are no introductions and main points and fun asides, just a mechanical, steady stream of words with much too frequent, quasi-randomly distributed fake "main points".
Also the training punishes clearly wrong text harshly compared to not clearly wrong text.
Which gives a relative incentive to hard to understand text.