Maybe i missed it, but that '70 'Cuda 'vert resto...I don't see it put on a rotisserie. If they aren't planning on it, then don't see what's wrong w/no bracing unless they start cutting off all the quarters and/or floor pans.
With the way they trimmed out the 1/4's so far...Maybe they can get away with it, but the complete 1/4 panel on a convertible and hardtop plays an integral part of the uni-body shell. with it sitting on loaded suspension, the rear end of the car will want to fold in, especially if the frame rails are weak.
Every shop restores cars differently , I've done a lot of major rusty cars, so I use the same format for all jobs.
In my opinion, the first step in any restoration is to completely strip the car and media blast, these guys who do rust repair to one area while the other areas are still covered in rust are completely crazy in my mind.