Thanks for writing about this. I was just getting ready to list my curated stories for Curation Matters when I noticed that the stats page does not list Topics for distribution anymore. The constant changing of rules on Medium is distracting and frustrating. Now I have to go into every published story that says "Chosen for further distribution" to check the topics it was curated under. And for future stories, I don't know if the chances of curation will decrease, as you have described.
Not sure how to respond to this change!