Guyon Racing made it in Calgary, 4pt bolt in and I didn't have it made it came in a car that was purchased. So I can't answer the harness question. However it wouldn't be hard to add a second harness bar. My guess it was for weight savings.
You guys seem to think bolt in is bad? I run a bolt in in the Miata and actually race it not hard park and it's perfectly safe on the track, and meets safety regulations. Also a plus that you can remove it whenever you want and install is much easier than having someone weld it in. That being said, any bolt in cage can be a weld in if you want it to be. Instead of bolting it in... weld!