I thought I understood it but now I'm not so sure. How to child themes in a theme framework work differently than traditional themes in a mutli-site network environment. Somehow I was imagining a parent theme with little individual child themes at all the subdomain sites. But now that I see it site directory, I'm realizing that there is just one installation of the child theme too, right? So is there any particular advantage for a network to use a child theme as opposed to single location sites?