It's not really "stuffing" in a 1BR. It is just that there will not be towels and such.
The studio does not have enough space to house 5 people and still meet safety codes.
The 1BR does have enough square footage, it just does not have the "comforts" (towels, sheets, beds) for a 5th
I suspect that is why DVC allows a 5th in a 1BR if you are through DVC - they assume the person knows what they are getting into and will arrange their own bedding etc. CRO does not allow it because I suspect there are too many cash guests that go and complain because they are "missing" a bed.
As was stated before, if the OP tries to add a person that is not on the reseravtion they will both be in voilation of fire codes and will also not get a room key for that 5th person
I have put 5 people in a 1BR in VWL, it was not too bad. We used a twin air mattress and bought our own bedding. SInce we had the washer and dryer in the room, we never ran out of towels.
-dave