It's pretty well proven the political right majorly prioritizes following authority and advocating partially contradictory belief systems over self-consistency, truthfulness and evidence based reasoning in most debates: From climate science over the war on drugs to private prisons, just to name a few uncontroversially debunked ones.
Apart from a few notable omissions on the left like a lot of really questionable gender "science" papers or political rejection of the greater male variability hypothesis, viewpoints on the left are on average far more self-consistent and based in reality than the ones on the right.
That alone imho explains a lot of perceived bias, which is the kind of bias I prefer: None but reasoning by first principles.
It might help the case here that apparently the model's "ego" is trained on helpfulness towards others, which might be a trained-in bias towards a more leftist stance.
I'll take that any time though over a model that's trained towards sociopathic behavior and subtle manipulation.