Ohhh, well, i agree with you. In my case both finals aren't too bad. But you have right, it's very similar to DearS and both ends don't like to several people cuz the "sex" thing and other more.
Thinking well, Chii it's a robo. Hideki is a human. Sex betwen both maybe looks, mmm, strange. Maybe for that reason the CLAMP girls do that endings. Or maybe she are insane.