Guido and Luigi, after a good vino with lunch, would come back to the loom they were working on and, finding they were out of one color, would pull something entirely different and finish the job with that.
ALL diagrams are just a suggestion, and while some of us do seem to find our cars pretty well matched to the wiring diagrams as published, others are not as lucky.
Your efforts to get educated are to be applauded and you must now spend another $65 for the CD, or $225 or so and buy "The Works" from the POCA club store. Everything published is there, including wiring diagrams. Your later car will no doubt vary from the earlier ones, but there will surely be some continuation - and remember, NONE of them are 100% right, anyhow.
Larry