I agree with your point of view. But, have you played Life With Mary? The developer of that game wrote that the game would not end just because the MC had sex with the title character. He has kept his word and issued several fine releases since then, with no completion in sight. Not to mention Babysitter, Dreaming of Dana, etc. Also, Dating My Daughter has reached the promised land, but is still in production, albeit slowly.
So, it is entirely possible for a developer to continue a game when the supposed main goal is reached. I hope, and expect, this developer will do the same, and continue on as you have suggested.