I'm sorry to say that I think they did right. As you say, there are already not that many Gold-specific advantages, but more importantly, I don't think there is any more reason to give 1A/K to a silver who will become gold again with this flight than there would be reason to give lounge access to a bronze who will become silver again after that flight or to allow a Gold to get a redemption in a revenue class where they will become GGL before taking that flight or a blue to reserve a seat for free on a flight which will make him become bronze again.

I would have some sympathy if it was a case of making an exception for something that really represents an emergency (e.g. some additional help for IRROP or something similar) but not for a "frill" like getting a specific seat.