I just tried the Emiglio theme and it breaks the entire site, nothing renders at all on any page. I'm guessing it's simply not compatible with the 2.x line of Omeka, but that says to me that it should be removed from the site as it's not functional, and really it's entirely destructive. I don't like the idea of playing Russian roulette with theme (and maybe plugin) downloads. If they are not compatible with the latest Omeka release, they should be removed until the author updates them, or all these themes and each version listed should actually be tagged properly with compatible version information.
The minimum version could probably be expressed more clearly. The target version tells what version it was developed to work with, so if your version of Omeka is greater than that, surprises could happen. The target info is the best guide to gauging whether it will work. The same is true in the plugin information.
Since there are plenty of sites that are not on the latest version of Omeka, though, we really can't remove it as defective. It just hasn't yet been updated and released for the most current version of Omeka. (In the case of Emiglio, it is currently being updated, and a 2.x-compatible version will be available soon.)