Yes, the code is dense, but changes to it don't make up most of the lines of diffs, and I really doubt the XML making up the diffs is edited as text; its a tool or generator.
I clarify this more above, but one of the reasons you don't see changes to that file is that much of the work of the repository was working on code that was deleted in favor of that file. And yes, the XML was edited by hand, as text, using ed(1). The vast majority of what I was exploring in the past I completely discarded in favor of that e.cd file that now represents the compiler.