Isn’t doxxing most of the time just collecting data from multiple public sources and connect them?

Maybe, but I don't think that distinction matters here. Surely you're not contending that it counts as doxing every time someone collects data from multiple public sources?

I've always understood doxing to be PII, which aliases aren't, AFAIK, unless they're connected to a real person. And, to my knowledge, everyone is contending that the names in the blog post are all aliases. And, regarding aliases, I've never understood it to be doxing for someone to say "FakeNameX and FakeNameY appear to be the same user."

So, to me, the thing that makes it not look like doxing is that it simply doesn't meet the basic definition of doxing. It provides no PII.

Yes, that is exactly what “doxing” almost always refers to. It’s a very disingenuous response.