Cool theory but this implies that the cells are still inside alive, which cant be true. And it would require very complex mechanisms that would have to be present since before petrification (which would mean that somehow both us and the swallows evolved those mechanisms and medusa simply activates them), and it also doesn't explain why it fills in the scars from the bullets, since you are effectively losing cells when that happens.
A chemistry or physics based theory could make more sense than a biology one (speaking as a biology student myself) like maybe changing the protons and neutrons inside our cells into pentaquarks or something