I don't think it's either indirect or complicated. It's just a file concentrating the FIXME instances that would otherwise be scattered and require a project-wide search.
Simple and elegant imho. That said, I wouldn't use something like that in a project without a build step that merge stylesheets together.
This is particularly easy to do in CSS because it is built up out of a set of rules that have no particular ordering or context. In a way, that's the beautiful part about the CSS. You can concatenate the files however you like and you can also pull out pieces from various components into one place. This certainly isn't possible in most programming where code behavior is highly dependent on the context that it is written.
There might be a subtle difference in the way people think about CSS vs. other programming that would push them to one solution or the other.
Simple and elegant imho. That said, I wouldn't use something like that in a project without a build step that merge stylesheets together.