"Rubber ducks float because they are made of a material less dense than water" both is wrong but sounds reasonable. Call it a "bad grade school teacher" kind of mistake.
Pre-gpt, however, it's not the kind of mistake that would make it to print: people writing about rubber ducks were probably rubber duck experts (or had high school level science knowledge).
Print Is cite-able. Print perpetuates and reinforces itself. Some day someone will write a grade school textbook built with GPTs, that will have this incorrect knowledge, and so on.
But what will become of us when most gateways to knowledge are riddled with bullshit like this?