The BCG you posted a picture of is a full auto BCG. If you follow the link I posted above you'll see how far back a "Semi Auto Only" bolt gets milled or in the case of the Colt Bolt I linked to, they completely removed all the metal.

If you look at the majority of ARs being sold, they have the full auto bolts in them. It's not a problem. I would be interested in the specifics of the case you referenced, to figure out if the BCG was the actual issue, or if there was more to the story. Or if they actually prosecuted, it's entirely possible that they didn't. Take a look at BCM's website, they are a well know AR manufacturer with at least 1 GOV and LE contract. They clearly market their BCG as AUTO BCGs and offer them for public sale. You can also go to STAGs website and compare the bolts they have for sale with the BCM auto ones and they are visually identical.

I understand why you are concerned, and you aren't wrong for trying to do your homework. I used to work for an FFL and the ATF boogey man was always on my mind.

What I recommend is to load that thing up with some 55 grain FMJ and go have fun shooting it.