If I was a loyal Skywards member and had paid a full fare for flexibility, I would be a little pissed if I ended up in a middle row because someone who'd paid half my fare got the last window or aisle seat.
Skywards members have advantage in their seat selection. That's one of the biggest privileges for skywards members. They have their preferred seat saved in the system, so system gives them that seat automatically when they check in. If their seat is taken by any chance, departure control usually meets their needs either by moving the pax seated at skywards member's seat to another seat or by giving a skyward member another similar or better seat.
Giving passengers who paid less than skywards members or who are not skywards members a chance to have better seats than skywards members by paying a few Dhs more undermines the whole skywards system, so of course "it makes sense".
Don't make a silver lining out of pure logic, Harry.