I don't see anything particularly unsafe about the way the brake away cable is fastened to the tow vehicle. As long as the brake away cable is slightly shorter than the length of the chains, so if separation occurs the cable reaches maximum length and then pulls the pin in the activation switch, I see noting alarmingly wrong with this set up.
I would not do it this way myself. I try to find a spot completely separate from the actual hitch to fasten mine. I use one of those D-shaped spring loaded key holder style heavy duty hook and latch it through the holes where the safety chains are hooked into.