

The phrase ‘reality has a left/liberal bias’ is just a meme stemming from how left leaning people usually at least attempt to base their world view on observable reality, and from various occurances over the years of far right figures complaining when reality (usually in the form of scientific research) doesn’t conform to their views or desires.
Those do however tend to be left wing which was the original meme before liberal became synonymous with the left in the US for some reason.