Thanks for your comments. In response to your questions, this article is over a year old now and I'd be quite confident in saying the 'unwritten' rules of Medium's distribution have changed in that time.
Since the beginning of 2021, there has been a shift towards more 'relational' content - mainly within the confines of followers. I suspect this brought a better balance between self-published and publication posted articles. Hence the changes you have seen.
The key with 'further distribution' is that it pushes your article out beyond your followers.
If you want to reach a bigger audience, then working out why articles were distributed is key. As you say, it is a rabbit hole you can easily get lost in.