Lumping all spa's into one group and comparing percentages to trad is, imo, not valid. You'd have to lump in all authors sitting in slush piles to make that chart even.
Yes, this is exactly right. Since anyone can self-publish, the comparison that has to be made is between all authors trying the self-publishing route and all authors trying the traditional route, including those who get rejection after rejection and never get a traditional publishing contract. Comparing the ones who succeeded in traditional publishing (which are going to be the top tier amongst all of those trying) against all self-published authors isn't an even comparison.