So they ended it with the cop out version of the novel. I'm disappointed. Different media are for different things to try. You can end your tv drama differently than you did your novel and your anime different than your manga. That makes the whole adaption thingy fun, but this... this feels just lazy and like a punch in your face to GET THE MESSAGE ACROSS the way the author wanted. I quite dislike it.
Angelic Layer did it right IMO with the different pairings in the manga and the anime. Get creative with this stuff and not stiff.
For the reader, who didn't know this was coming, it must have felt like a punch in the face and a big F*CK YOU. You have my condolences. This ruined a perfectly good manga and not in the 'Let's think about it' good way.