It's not about the number of books, when it comes to collaborative projects, its about the number of writers. Every writer has a different style, uses words differently to mean the same things, different things, similar but not same things, etc. That's why most companies set up the standard terms before they start work on a project. Add in the Shadowrun custom of copy/paste from older editions (which had no standardized definitions) and in just compounds the issue since they didn't start with standard terms.
Honestly, it would probably be easier, faster, and cheaper to create standard terms and rewrite the book than try to errata it to fit to a newly created set of terms. That would take a good editor though (to be cheaper at least).