parkrun has been very strongly inclusive of trans folk, so they aren't likely to fold easily to this sort of stuff. They consulted me as part of their 2019 overhaul of the way they handled gender, specifically because they wanted to hear trans voices.
I've spoken at one of their regional conferences, and they even stuck my rambling on a video on youtube to highlight what inclusion looks like https://www.youtube.com/watch?v=HoFMav9G8vs