@Brefugee if we received a verbal complaint about a transwoman being the first female finisher or showing up as the female course record holder, as a run director on the day I would complete the incident form when processing results saying that complaint had been made. If it was emailed in, our event directors (they're the ones nominally "in charge" of our event) would pick it up and again I imagine email the complaint to HQ.
It's a complaint about official parkrun policy so we don't have any leeway to change anything, or to really comment about why that rule is in place.
For what it's worth, 99% of runners at our parkrun probably aren't bothered by the course records - most probably don't even know what they are! People really care about their own PBs, if you're pushing hard it's great to get an email saying congrats on your PB. Our men's course record was broken by someone visiting from up north last year, a really great runner who smashed it by 30 seconds. It's now far out of reach for all the local high level club runners, but they still come along and it's great if they can get a PB for themselves even if they are unlikely to get a new course record.