You're not entirely understanding how these builds get compiled.
So, they have this source tree, right? There are all kinds of modular parts to CM7, or any ROM. But because CM7 is built for lots of phones, not every phone uses every part, and some parts are specific to certain phones - for instance, all of the CM7 phones use the ADW launcher APK. And the settings file. And.. well, you get it. But only the DX uses the DX drivers. It has a special build.prop. And the DX doesn't use files that might relate to, say, a front facing camera.
Rather than recompiling everything in tidy little packages for each phone, you use a system wherein each phone has their parts selected and those parts are compiled into each phone's build automatically. That includes the changelog.
The consequence of this, is all of these builds really have nothing to do with the Droid X, even though the changelog marks stuff. They're part of the whole CM7 source tree, so other developers are fixing stuff for other phones, they just happen to be files the DX uses too. Actually, some of the stuff does relate to the DX, but you're looking at it as "why are you fixing minor crap when major crap exists?" whereas the developer is saying, "droid X what? I don't know squat about that, this fix was something I noticed on my Nexus One."
Make sense? The devs for CM are working on all kinds of phones, and some of the CM7 builds are super stable and full featured. So when you see changes, it's only because there were changes to files the DX happens to use in its own branch of the source tree, and they may or may not have a visible or important effect.
