Tyler.
Since he is looking at building more a Pro-Touring type car, the car needs to be more ridged in more ways than just launch. So if you connect the frames together, from the side as well. The car will have virtually no twist what so ever. Plus, he has his cage tied into the subframe. That way the car is even more solid and if the unthinkable ever does happen, the car will hold up allot better as the cage isn't just bolted/welded to sheet metal.
And let me say, after seeing the car in person. That whole set up looks very nice and sturdy.