Hear, hear!
Call me a little bit cynical, but I sometimes wonder if Medium itself even knows how things are currated. Putting on my hat as a programmer, I imagine this curation process as just some bloated AI that they run in the background that has bugs they haven't fixed in a couple of years.
Who is to say that the curation AI doesn't also include some randomness in there just to keep us writers guessing on our toes. If the curation formula was found out and defined, the intrigue would be gone.
The fact that they don't really give us a firm answer speaks volumes imho.
*Steps off soapbox* :)