I think 'gender disappointment' is very different to having a miscarriage or losing a baby (I have miscarried and it was devastating and theres no way it can be compared to not getting the sex you hoped for). It is not the same thing at all and although it comes across rather self entitled and pompous when someone says they prefer either gender or are 'devastated' about having a boy or whatever, I do believe their feelings are still valid and there is often deep subconscious psychological reasons for their feelings. I think its actually quite common for people, particularly women to be disappointed by a certain sex, it seems to be mostly boys from my experience. However in RL it is not acceptable usually to say anything.
I am having a girl this time (its my first) and the only thing I was interested in at the scan was if the baby was healthy, the surprise of what sex it was was just a pleasant after occurrence. I have to say I am glad I'm having a little girl but only for the baby clothes, she might well hate pink etc when she grows her own mind!
SIL, the same age as me who had her first who is a boy last year and never seemed that happy about the fact he was a boy, has shown her obvious jealousy and has said 'I'd like a little girl at one point' several times, I did think what if you never have a girl? Many people don't. I truly think some women do have a deep longing for a little girl and it is usually for the wrong reasons (want a mini-me, want a best friend, don't want to be the dreaded MIL, worried about the fact their sons may have a wife/gf who comes before them one day and other rather selfish reasons)
Have a look around the internet and you will see how common it is for women who only have boys to be disappointed and feel something is missing in their lives. It is very sad IMO, particularly for their little boys. Its very selfish I think to keep having children in the hope of having either sex one day. My DM had girls only, her 3rd and last pregnancy being a surprise and she has admitted to us that she was teary for a week upon finding out the last DD was another girl as she knew it would be her last one. I honestly think it is very common for people to have preferences (but I think with DM she would have just liked to have both), funnily enough my mums youngest DD was the apple of her eye and has been a right mummys girl ever since she was born, she is also the most like DM and they get on the best out of us all and DM has said once she saw her she wouldnt have changed her for the world, so I think its unusual for someone to still care once they have their baby. DM has said though that she much preferred 3 girls which she got than 3 boys, no idea why that was.
I do think there is much more to it than the woman on OBEM being purely a selfish idiot, to feel that way is very common I find although I accept that its hard not to judge especially when you've have previous losses and would just love a healthy baby! xx