This is not correct, Medium specify in their help article about how earnings are calculated in the MPP that listen time is counted. https://help.medium.com/hc/en-us/articles/360036691193-Calculating-earnings-in-the-Partner-Programis

Further I agree with the quote you share from Tony Stubblebine, I don't see it as Medium's job to give me a full time income. I see it as my job to earn a full time income. I believe if you work at it in the right way on a consistent basis you can earn a full time income from Medium. But I also would not advise doing that necessarily either. When you are dealing with incomes such as from Medium it is better to spread your income across multiple platforms. Because you never know when one is going to disappear.