I agree that the issue of how to treat cis-women and transwomen at competitive races is a complex one where debate is needed and quite possibly extra categories. But parkrun is not a competitive race.
Why is it complex? Transwomen are men, and should compete in the male category. Male puberty confers a myriad of physical advantages that are not negated by taking oestrogen (assuming TW even go so far to transition; many do not). Teenage boys can beat elite female athletes’ records once they’ve gone through puberty.
Why should fair competition for women take second place behind validating men who don’t like to be thought of as men? Why do their feelings trump fairness for women, when there is already a category they can compete in which doesn’t involve cheating?
Sports are sex-segregated, not gender-segregated, and it is not possible to change sex however much one may wish it to be so. Therefore one should compete in the category that is for one’s natal sex.
I doubt Paralympians would be overjoyed if able-bodied elite athletes started identifying as disabled and setting new records; it’s the same principle.