Since you wrote about your experience, I'll write about mine - which is very similar.
My first curated story on Medium was in gaming with a small publication (you know this publication). My second and to fourth curations were also with the same publication and within two weeks I got top writer status in gaming. After that, every story I wrote about gaming (either with this small publication or self-published got curated).
Later on, I noticed that all my stories about tech are getting curated as well. A month later I got top writer in social media (not a single post of mine is about social media) and in Technology.
Now, any post of mine about tech is immediately curated. One wasn't which talked about AI in the Arabic language. I guess it wasn't curated because I wrote one Arabic sentence in the post, and the curation algorithm just kicked it out because the curation is only applicable with English at the moment.
It is even funny I have my own publication about finance. Once I posted a story to it and it didnt get curated. I deleted the story and re-posted it again but as self-publish, it got curated immediately and after that I added it up to my publication. It seems that Medium still doesn't trust my publication to be a reliable source, but it trusts me as a writer.