While I agree with the main message of your post the mathematics behind it are incorrect. That's pretty irrelevant but let me explain what I mean. When you spin, you have words or n-grams that repeat themselves within a block. In other words you will have:
{was going|will be going|am going}
While you have 3 different options, each of them uses 'going' which in turn has high changes of producing a similar partial n-gram.
That aside, even simple 1-level spinning can produce thousands of articles and still remain at around 40-50% uniqueness. I did a test -
check it out here.
Using multi-level spinning will not only increase the number of articles you can produce but more importantly it will increase uniqueness score. In other words, the only way to increase uniqueness is to use multi-level spinning. Even if you spin just 50 times, uniqueness of articles generated from a 1-level seed is still the usual 40-50%.
Now, when you do 3-level spinning (paragraphs, sentences, words) you increase uniqueness and the number of articles you can generate. However, the number of articles you can generate while high, it will reach a tipping point where uniqueness will start to drop from the usual 70% to lower. However, it will remain above a certain uniqueness (in my experience never drops below 30%).
All the mathematics however is irrelevant. Why? Because Google doesn't use an algorithm like the one used by CopyScape - that would be too processing intensive. While Google can figure to a certain degree how similar several pages are, id doesn't penalize you because they are similar. That's teh reason why crappy content, poorly spun or downright stolen from other sites, ranks just fine if you point some good links at it. Authority is a much important factor when deciding the SERPs. That is why while all news sites basically have the same information, only the authority ones will rank high.
I do, just like you, recommend multi-level spinning. I have absolutely amazing seed articles (tens of thousands of words). As a matter of fact over the past year I have produces over half of million words worth of spintax. That will cover my content needs for this niche forever. However, I consider the detail of the math as you present it are incorrect. Again, it is something irrelevant in practice, though.
You might also want to read
this post of mine.
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