It has nothing to do with anything, from what I can see.
I just spent the last hour crawling cars.com listings for 2012 Foci within a 30 mile radius, looking at engine bay photos of cars, and looking for the tell-tale sign of the thick vs. thin bolt spacers for the strut mount bolts.
I wasn't scientific enough about my process that I wrote my findings down, but I did find SELs and SEs with and without the thicker strut tower bar. Some dealers were generous enough to include photos of the build sticker in the door jamb, so I could see production date, and many of the ones that I saw with the reinforced strut tower bar, had early 2011 production dates. Many, unfortunately, didn't include photos of the build sticker, so who knows when they were built.
I also did find the odd car here and there produced late in 2011 with the reinforced tower bar, but the majority of them didn't have the reinforced strut tower bar.
I know there were several supplier issues with some of the Job 1 2012 Focus production, so that could be a potential reason for the strut tower bar variation. Otherwise, I have no idea.
Joined the dark side.