However, they didn't restrict participation to one sex, so it's not clear that that applies.
I suspect that the goal of that section is to allow charities to fund raise in a way that reflects their purpose, which may be for the benefit of either men or women, but this fun run was for a range of charities.
I think it's interesting that the people organising the run didn't quote that section, but quoted the rules that allow single sex swimming sessions, organised on religious grounds. iI's not clear what religious grounds there are to exclude women from a fun run in a public park. It would be interesting to hear an explanation.