Likvod Harav Shlit”a,
Seeing as we know that the understanding of some Rishonim that eating while leaning on the right is dangerous was based on a mistaken understanding of the location of the windpipe and foodpipe (kaneh and veshet), and we are therefore forced to explain that the sakanah was only said in regard to one lying on his back (as per Rashi Pesachim 108, and contra Rashbam) should a “lefty” lean to his right (the more natural position)?
No, even a lefty should lean on his left side. The Mishna Brura brings an opinion [472 Shaar Hatziyon 13] that even a lefty who leans on his right may not fulfill his obligation, even bdieved.
When Chazal rendered a halachic ruling they were intended to do so with their understanding of nature, biology and the physical world. Their rulings then become part of Torah Shbal Peh. This was the intent of Hashem when giving over the ability to make halachic rulings to Chazal. This was never intended to line up with scientific knowledge. Scientific knowledge by its very nature is dynamic, constantly changing with new discoveries and advances. Torah is the ultimate unchanging mesorah, so once Chazal established the halcha it doesn’t change based on scientific knowledge which is a totally different wisdom and set of rules.
This principal idea is the key to understanding the general question of Torah and Science.
A an aside, even from the scientific side of things, we only accept proof after experimenting and proving, ie. the scientific process. To the best of my knowledge no study or survey was ever done to prove that leaning on the right is just as safe as leaning on the left. While we don’t see a reason for there to be a difference, this would be our unproven theory, well based and logical as it is.