The site, in very elaborate ways, is saying that Stage IV cancer (in the author's words 'tumor has spread to distant organs or lymph nodes') is worse than Stage I (localized) cancer.

I don't think there is any person who is aware of the idea of cancer mortality who would equate 'Stage IV' to lead to 'average' survival.

So maybe the article's only point (which is very obvious, and does not require Markov modeling) is that if you increase the number of people who live a long time in a sample, then the average of that sample will go up.

This feels like someone saw a fact on the internet and didn't try to read about it before writing a blog post.