Staff only advised to check again later - which pretty much confirms they'll only fill up planes instead of offering loyalty awards.
Anyway, I sent them the following and will update you about the reply.
Regret to say I fail to understand. As a loyal client to your airline, the past year I have flown 20 flights in Business Class, as well as 4 flights in First Class.
At the moment there are min. 6 seats in First Class available on the flight for which the awards were requested.
In the terms and conditions it is mentioned that upgrade can be executed if seats are available, which seems to be the case.