We got what we wanted every time as Gold/Plat. They have to honour it because they want to avoid the $100 compensation.
Have you checked your bed preference as default? It's because we set ours as Kings but then when we are out with kids we have to manually change to 2 doubles.
Sometimes you get a better chance for upgrade if you can live with 1 bed. That happened to us at Leipzig Marriott - we checked in with requests for 2 doubles and then Mr. Nacho asked for upgrade possibilities. They said they don't have 2 beds upgrade, so he asked what if I can live with one. He got a studio as an upgrade.