Depends how one sees the world... purchasing a first class ticket and turning up at the airport at the correct time, one could reasonably assume to travel first class and receive first class miles.

Travelling first class was impossible, but receiving first class (bonus accelerator) miles is still very possible.

I agree that it is standard airline practice that no refund is due... as the mixed class journey cannot be ticketed for a lower fare. This does not however make 'sense' to someone receiving less service than they have paid for.

If you agreed to pay somebody a sum of money in return for a BMW and a free tank of fuel, paid the money and turned up at the collection point to find that the only vehicle available was a Fiat... even if you accepted the Fiat in place of the BMW without any refund (due to an urgent need for a car) would you consider it reasonable that the tank of fuel also be withdrawn?