Hi, thank you for your insight!
However, when Adnan reaches the threesome scene he's still in the common route and has never thought of Halim as other than a friend, no matter if he has opened up to him more or less, depending on your choices. Their feelings for each other don't take a romantic turn until his route has already started. During the threesome, there aren't really romantic vibes: by that point, Adnan is fond of the two of them, but nothing else.
The common route is exactly that, common, so of course the scenes will happen regardless of your choices. The affection points are only important to branch the game at a given point.