That'd be cool, but it just uses publicly available APIs for this. Most of the data like that isn't reported through the public APIs across various types of software. Bad data is tossed out (e.g., the you-think-your-fake-numbers-are-impressive.well-this-instance-contains-all-living-humans.lubar.me lists over 7 billion accounts) but data that is (as far as I know) accurate is presented as-is.
Looks like you are correct, yeah, and the raw logs show 7,410 of the 10,729 live instances have it. Lemme hack it in real quick; I can't put it onto the big pages and not sure how well adding another column to that table will work, but give me like five minutes.
It still has joindiaspora.com at #4 which is not even active anymore.