I think it's a combination of maturity and capacity for destruction. Even though Gracie laughed at baby gates, it's much easier to puppy-proof a room (or even a house) for a small dog.I can practically feel the magic from your pic!
I wonder if there’s any difference between the size of the dog and when owners start giving more freedom. I know that smaller dogs are supposed to mature faster than bigger dogs. Say you had Peggy at 25 years old. Do you think there would be a difference between when she started to get more freedom compared to Gracie?
Oh my god, I can imagine Gracie going from tentatively pulling off one strip of wrapping paper to just going ham and a flurry of paper and bows flying.
I think the fact that Gracie didn't actually destroy any of the gifts themselves was a testament to her maturity. But even small dogs can struggle with impulse control well into their first few years. I saw a huge shift in Gracie at 3, but ages 5-8 were like a human's 30s: Maximum maturity to health ratio.