Unfortunately the wording in this section doesn't explain what an "inappropriate mixed-sex sport" is. The Gender Questioning Children guidance went further on this and it's a shame that that has been lost.
As an example, my daughters' school thinks it's entirely appropriate to make all PE lessons mixed-sex. They say it fosters inclusion, completely ignoring the fact that many girls (as some parents have told me) feel excluded because they don't feel safe.
Eventually, the school decided that in football lessons they will separate by sex in the higher ability PE set. When I pointed out that lower ability boys also posed a risk to girls because of the difference in their physical attributes (particularly from puberty), this was ignored. It seems obvious that a boy of lower ability could be even more of a risk in some ways, as he doesn't have the skills to understand how to approach a tackle etc.
It's a good example of a school removing single sex provisions - all PE lessons used to be single sex in this school - as a way to both meet the law and (should they wish to do so....) to continue to obfuscate on the difference between the sexes. It leaves space for schools to pretend that this difference really doesn't matter, even where it impacts issues like safety in sport. Thankfully, the guidance makes it clear that they can't extrapolate this logic across to changing rooms, toilets and residential accommodation.
But it seems like safe access to sport is no longer a requirement in school.
The KCSIE and other (e.g. "gender separation in mixed schools") guidance on mixed-sex provision in school sports leaves it entirely down to the school to decide what is appropriate when it comes to safety.