Do these models really lie or do they only do what they are supposed to do - produce text that is statistically similar to the training set, but not in the training set (and thus can include false/made up statements)? Now they add another run on top of it that is in principle prone to the same issues, except they reward the model for factuality instead of likeability. This is cool, but why not apply the same reward s…
They really lie. Not on purpose; because they are trained on rewards that favor lying as a strategy. Othello-GPT is a good example to understand this. Without explicit training, but on the task of 'predicting moves on an Othello board', Othello-GPT spontaneously developed the strategy of 'simulate the entire board internally'. Lying is a similar emergent, very effective strategy for reward.
You can't lie by accident. You can tell a falsehood, however.
But where LLMs are concerned, they don't tell truths or falsehoods either, as "telling" also requires intent. Moreover, LLMs don't actually contain propositional content.