Not to worry. I think this is a glitch in the Personalizer software. Same thing happened to us. I called Princess directly (1-800-PRINCESS), asked for a correction, and a few days later the Personalizer showed Queen bed.

I think there might be just a few quad rooms on the ship that have twins not able to be converted but usually the ones listed in the Personalizer as "non-converting" can actually be reconfigured as a Queen.