Looks like they are referring to the BAD Lever from the description in the article and not to the quick change capability of the ACR. If something else holds up the ACR, you have to wonder. But, Cerebus has deep pockets, so this could be a ploy for licensing fees.
There is another company selling a BAD device, and it seems like a copy of Magpul's design. It is interesting that Robinson waited until days before SHOT Show to file this lawsuit, when they've had to know about the Masada/ACR for a couple of years. Although I am not a patent attorney, I do know that you have to defend your patent if you know (or suspect) that it is being infringed, i.e., you can't sleep on your rights. Also, just because there is a patent was issued doesn't mean the patent is valid.