Your guess is as good as mine haha. I'm the second owner of the car so I don't know the full history. And Yes its a 2010, and there is nothing to match on the other side. I also agree with some sort of anchoring point. I looked at an MKS and it did not have it. I originally thought maybe from an under panel, but doesn't look like they come with any.
I was also thinking it could be left over from manufacturing if they use these on a Jig during assembly of the car/frame. It has the same square hole in the subframe on the other side but no stud.