its completely in the incentive to include such examples in RLHF. or you have come up with a way to increase performance that the very employees haven't. why do you think they didn't try it?
To train this effectively you would need a dataset of questions which you know the model doesn't know. But if you have that... why not answer the question and put in the dataset so that the model will know ?
That's a bit imprecise, but I think it capture the idea of why 'I don't know' answers are harder to train.