Just thinking ---
One situation would be is if someone booked a room or package as a passholder,
AAA, FL resident, or whatever requirement. And then could not produce the required documentation/membership card at check in.
Supposedly then the person can be charged rack rate.
I assume the guest checking in would be informed at check in. (And assuming the guest did not say they will bring the required document, but never do.)
I am sure it happens. I just do not know how this works personally. And don't recall off hand reading of anyone's experience on the Dis.
I recall probably 5 or so years ago on Disney's internet site a severely incorrect amount being allowed to book for a deluxe resort. (Think it was BW.) Once the error was found by Disney, they corrected their rate and did not honor what was booked under the ridiculously low rate. (Seems like it was $1 or something like that.)
So there are cases. But I would think few and far between. And they would be covered legally I am certain. And there are probably other situations that happen few and far between.
As far as confirmations go, from my personal experience, those are not worth the paper they are printed on. I look at those as something the traveler should review to make sure they agree with what is listed. (They booked what they thought.)