"It’s well-known that all leading LLMs have had issues with bias—specifically, they historically have leaned left when it comes to debated political and social topics. This is due to the types of training data available on the internet." Perhaps. Or, maybe, "leaning left" by the standards of Zuck et al. is more in alignment with the global population. It's a simpler explanation.
I find it impossible to discuss bias without a shared understanding of what it actually means to be unbiased - or at least, a shared understanding of what the process of reaching an unbiased position looks like. 40% of Americans believe that God created the earth in the last 10,000 years. If I ask an LLM how old the Earth is, and it replies ~4.5 billion years old, is it biased?
It's hardly biased, it's stating the current scientific stance over a fringe belief with no evidence.