Yeah, you're right. I already have a bar going between the strut towers in back, but since I have the Focus Central coilovers (coils directly on the rear struts), I wanted to try something different. A lot of stress goes to the tops of the strut towers.
My plan was to get one of those BRP bars, and then have cross members welded and then bolted to the strut towers.
That way I'd have the strut towers linked, AND the tops of the strut towers linked.
It's not urgent, I'm not noticing anything wrong. Just something I've been thinking about and would be a neat little project.