Most of this discussion has been theoretical, but I can tell you as a practical matter that I have made over 200 pizzas using this method and the flavor is light years ahead of any thin or cracker I have ever eaten.
I think the key elements in your case were the use of a lot of starter and a small amount of commercial yeast. And, to be honest, if it weren't for the fact that Prof. Calvel had discussed the use of both a natural starter and commercial yeast, I would have thought long and hard about posting on the subject, even when I knew that others were doing the same thing, as I earlier noted. But, even in Prof. Calvel's case, he recommended the combination of starter and commercial yeast for the cooler months of the year, from September to May. That implied that the reason for the commercial yeast was for leavening purposes, as a belt and suspenders solution, not for flavoring purposes. But, even then, he was careful to note that the amount of commercial yeast should be small.
In your case, you used a lot of starter, 20%. When I played around with natural leavening systems for various types of pizzas, including cracker style pizzas, I, too, used around 15-20% starter. That amount came from a forum member who was a baker (and still is) who used natural leavening systems for making pizza. I suspect that the dominant flavor contributions came from the starter rather than the commercial yeast, although I defer to the opinions of those who have done more testing on this subject than I. That is all the more reason for Norma to test using combinations of natural starter and commercial yeast, given the vast range of her pizza making experiences and having developed strong opinions on what seems to work and what doesn't and what she likes and doesn't like.
FYI, another good example of the use of a natural starter for a cracker style dough is discussed at http://www.pizzamaking.com/forum/index.php?topic=21326.msg214946#msg214946
. In that example, bakeshack (Marlon) used 20% starter (but no commercial yeast).