Nah, there is a bit of a space, but it's very small - too small for our torties to fit through. Combine that with the fact that tortoises are wary of ledges above a certain height (about 4 inches or so), and you get a very safe porch. It's more just to prevent accidents.
One of these days I'm going to get a picture of our tortoises acting naturally. You should see how he looks around, like he's very curious about the environment beyond the balcony. When I took this pic, he looked back because I had distracted him. Still very cute, though.