I called MPC recently to book a V-class on a HKG-KHH flight - they told me it was sold out and that, even as a MPC gold, I could only book into L class. I thought that was odd and declined it (and just used some Avios miles for the short hop instead). She told me specifically that the seat guarantee was just for an economy ticket, not for a sub-class?

Prior to this, my understanding was that as long as the class was offered on that flight, even if that class is sold out, the seat guarantee would give me that class at that fare price? But this recent experience seems to be no? Or maybe this is just changing?