Well, in that case, obviously no, but it's not always the case. You can have multiple non-Melody endings in "Melody" for instance. Or for incest games, the path to be alone with your sister in "My sister, my roommate" is pretty tedious, and is more like a bad ending (or to add her in your possible relationship, you have to actively destroy hers).
No offence I can see your agument but if i may just a couple of things.
There is a suttle diffrence between Melody's and Haley's game namely the part where Melody's is just that "Melody" but Heley's is acttually "Haley's story".
Not much diffrent I grant you but it do's rather imply that the game is primarily about and involving Haley to a much greater degree than that implied by a game just called "Melody".
On top of which Melody although contains a girl called Melody to me atleast seemed like it could just as much of been called Melody as in the a musical term.
Because of all the musical reference and the musical information it contained and there was a fair bit of that just as easily as it being for the girl herself.
And the second thing is you mention is "My sister my roommate" but if I remeber correctly that game although it had incest in it that wasn't initially the main focus or Idea as an ending, we were never meant to hook up with the Sister at the End.
And it was only because so very many players requested it that the Dev seemingly but grudgingly added that as an option.
But the point is that out of thoughs three games Haley's Story is the only one that acctually can be said to refer to the girl in it and hint's that it is focused on the Girl in the title spercifically as the LI.
But of course thats just my opinion