I'm a female former senior employee of a large organisation. I think your boss needs to demonstrate how his choices are right for your firm, evidence is one thing but essentially the best appointments in any team are putting the people most qualified and suited in role regardless of their background.
I also think that the number of women in senior roles in any organisation should at the very minimum be reflective of the approximate ratio of m/f staff. If should be an inclusive environment where opportunity is available to all, ambition is encouraged, the process is transparent and promotions are awarded on merit and talent.
I think if the right people are put in post it's obvious to all, again regardless of background. These questions often come up when someone better could have been appointed and has been overlooked, do you think thats the case here?
I think having a structure which is mindful of the importance of visibility of senior women sends a very clear message to an organisation that it is an equal opportunity employer, but I am also very much against over promoting people just because of a target based model. I know of people who made background (I won't be specific) a key feature of their business case and threatened to leave the organisation to pursue opportunities elsewhere if they weren't promoted. Needless to say they ended up vastly under experienced for the position in which they found themselves and left the organisation before getting into trouble.
Likewise, I think it depends on the type of woman who is being promoted. Just because someone is female it doesn't mean they're going to be a good role model for all other women. Likewise, I have know many male managers who have been huge advocates for empowering women and facilitating a good work-life balance as much as possible. Some of my best bosses have been men - it's the type of person that matters too. One of our most senior women famously returned to work four weeks after having all three children to work all hours, whilst her husband took on the role of stay at home parent. The other female managers were mostly women who for whatever reason did not have children and found it difficult to identify with the experience some women had.
So to make a chance in your case you need to be identifying women who you think have been overlooked and championing their case for senior management, including yourself if need be. I agree with you though, it sounds in principle like it really is a missed opportunity.