If ED had been the second woman to object to Upton in the changing room over concerns that it wasn't equality, would it have encouraged other women in the department to speak up.
ED is responsible for her own position. She was in a position of more authority and it would have been harder to suspend her and to retrain her, if she was doing her job in understanding equality AND safeguarding.
She has said by her own admission, that she might have taken a different tact and said no to Upton if there had been more opposition.
Therefore she wasn't actually taking the Equality advised policy route at all. She was taking the path of least resistance and would give her an easy life. And she was able to do this because she knew damn well she had an imbalance of power and everyone else felt intimidated by management on the subject - everyone junior was in no doubt she was TWAW from her framing.
Her framing was 'in order to make Upton feel welcome, we should accommodate him in the changing room. If you have a problem with that let me know'. Therefore by default saying if you didn't accept it you were considered as being unwelcoming.
And therein lies your issue.
ED wasn't neutral and ED made her opinion and that of managements clear to junior staff.