I've now come across three people who are not affected. It appears to me that they become affected if they write about Medium because the people who read the Medium stories are those who read a lot on here, and so their money is split many ways. When they revert to their core topic, the money goes up again. This backs up what Tony says.
The thing I reckon I am going to struggle with though, is getting different eyes on my stories from outside of the echo chamber - because there's an obvious lack of distribution on wider topics. I don't know if I will be able to break through that barrier to distribution.
For example, my stories on Parkinson's disease are not being circulated to people who are interested in Parkinson's disease. It's pretty common, so you might think there would be a section of the readership who would be interested. I don't know. Maybe I'm in the wrong place if I'm not writing tech.
On that note, I thought I might try writing more tech, but historically, the only people who have read my tech stories have been the usual people - they're not reaching a wider readership. Then we are back to distribution issues again.
I wrote a great piece about legal changes and non-compliance in solar panels, which was nominated twice, but it wasn't boosted, and failed to find an audience. That was tech, and it was good.