The 'parkrun' question isn't about how many males take the records or positions of females .. it reinforces the narrative that women, women's sporting achievements and the participation of women in sport are less important than men's right to identify as women.
The 'parkrun answer' is not to do away with categories, to have sex verification or policing of categories.. it is about changing the language in the rules.
Instead of 'we publish results based on a person’s self-declared information, including gender.'
'We publish results based on self declared information including sex. The category 'prefer not to say' exists for those who wish to use it. Records and rankings will be published based on sex categories only. '
or even...
We respect the rights of participants to view their results under the category of sex or under the category of gender. Participants are invited to enter their details under both categories, with 'prefer not to say' as an option for each. Results can be segregated by sex or by gender as per individual preference.
This would balance the requirement of both groups.
In reality, very little will change. If there is a clear attempt to circumvent the rules, any question would be dealt with quietly within the stated rules which includes a statement that participation includes an agreement to abide by the decisions of the organisers... and if a dispute process were required.. they could choose to have one or could write a policy about this.