I think you have misunderstood my point.
We understand that some women can't comply with the dress requirements of their religion and attend mixed sex swimming sessions. Swimming costumes are necessarily more revealing, so I assume that there are reasons why non religious women might also like single sex sessions.
However, if that is the reason for banning women from this event, the suggestion is that women can't even walk or run in public. That is the opposite of an inclusive event.
If, on the other hand, the suggestion is that this race was the equivalent of a single sex swimming event, then that is a load of old cobblers, because, as you say, it took place in full view of anyone who happened to be in the park.