At this point, it's a waiting game.
Iberia risks losing quite a bit here beyond any sort of monetary loses they will incur with this promo.
If a company clearly and emphatically states multiple times it will do X (9,000 Avios per flight, on one-way flights, no requirement to fly the tickets booked) then any customer that participated should be entitled to the full AVIOS per their own terms. As a supplier, vendor, partner, investor, end user or even employee - if reflects very poorly on Iberia if they refuse to honor their contracts - doesn't matter who it's with. End of story. Loss of good will is something that is hard to quantify, and easy to lose.