My children - 1 male, 1 female both attend the same co-ed state grammar school and I can honestly say I've seen no bias towards boys (or indeed girls). The school has a roughly 50:50 split between boys and girls.
PE lessons are mixed sex but games lessons are single sex.
Boys play football, hockey, rugby, cricket
Girls - football, rugby (contact), hockey, netball and rounders (although there is also an option for girls cricket).
Both girls and boys row although train on the water on different days.
The school has a reasonably high number of children who are selected to play at international, national and county / south of England level.
My daughter (a netball player) certainly doesn't seem intimidated by boys and doesn't modify her activities due to their presence. She wears a skort and depending on the weather leggings (there are tracksuit bottoms but neither girls nor boys tend to wear them favouring base layers). She certainly doesn't seem body conscious as she will wear the skort for most of the day sometimes depending on timetable/ matches and then wears it home rather then getting changed.
The only thing I can really think of which was a bit off was that the girls were originally told they were playing touch Rugby - they complained and so play contact. The deputy head played Rugby internationally and coaches the senior boys team (the DH is female) and all the boys (and girls) have huge respect for her (she is a history teacher btw).
I think it's great that it's co-ed - they have respect for each other's sports - e.g. Cheerleading where there are a number who compete internationally- my son admires them as athletes whereas in an all boys school he might dismiss cheerleading as not a proper sport.
What does make the difference is the culture of the school and the high calibre of PE staff - they have international players coaching in rowing and hockey in particular. The head of PE is a woman.
So yes I would agree with the article.