You're right upgrades usually apply to same catagory rooms just a higher deck, but in our case our daughter was upgraded after we received our docs. She booked a cat 6 guarantee and when her docs arrived she had a room assignment on them a cat 6B room. We received a call about a week before we sailed to tell us she had been upgraded to a cat 8B balcony room. I have no idea why she was upgraded but they put her on the same floor as our room and our sons room. Whatever the reason we were very pleased with the upgrade. We had a great cruise!