In a swimming pool I used to use the single sex changing room was a range of cubicles with locks on the door and gaps top and bottom. Same as is in my local pool which has gender neutral changing.
In another I've used that is gender neutral it has a mix of cubicles with top/bottom open and floor to ceiling lockable options for changing.
What is the point you are trying to make?
You have two different mixed sex changing options there with different risks. Because of the known problems with voyeurism, which is male behaviour, the temptation is to make changing room cubicles with floor to ceiling privacy. However, it’s difficult as I said before due to chlorinated water and also ventilation and cleaning are much easier with floor to door gaps so it is unusual for any design to be floor to ceiling in a swimming pool area.
So basically women have to put up with a huge amount of voyeurism in mixed sex changing rooms when there’s door gaps. However, if there’s no door gaps, it’s worse for health and safety for both sexes. These are the designs to tell your son to avoid if he has a choice, whether it’s mixed sex or single sex.
There’s subtle differences between changing rooms and toilet cubicles. Mixed sex toilet cubicles aren’t allowed to have door gaps, presumably because of voyeurism and discomfort. It seems bizarre we have mixed sex changing rooms where it ‘is allowed’ supposedly.