I have had many times a blocked empty seat even the plain had been totally full. It is a nice compliment.
Still in some other times it has not been notified.
Seem to be up to the staff who does the seating on the plain and/or the check-in staff.

I'm flying AY069 tomorrow monday having asked upgrade which has not been confirmed yet. Hoping some business no-shows and nobody else having Platinum in the upgrade queue.

The Customer Service told me that they are unable to see the waiting list even they for sure have been able to do that earlier. I asked the service guy is she not able to see that or is she not allowed to tell that. She said she could not see.