Sorry you're right, on that aspect I was mistaken. But the caveats listed in the thread and the weakness of the assumption of a uniform distribution in each bucket makes it difficult to draw any meaningful conclusions beyond what the original article had. That is, I don't think the mean is useful at any level.
the article's main message that being in 19% is an easy target is based on the mistake brudgers discovered; namely 25K in 4 years, or <10K in 1 year is barely a good target for any company or indie developer.
that's a presentation trick from Apple, mainly not telling how much developers get in current quarter, but rather bragging about a rolling number. the blog writer was a victim of the apple trick of rolling the revenue given to the app devs back to the beginning of the known history.
"Before reading the rest of this post, bear in mind that these numbers are not necessarily accurate, and may not be representative of other categories in the App Store. However, if they were representative, the back of our napkin would give a very different split from the default assumed position:"