Note that the author specifically mentions this and writes about using it for new posts and then falling back to selfhosting.
That way you can own your data and serve more visitors.
Sure, you can own your own data but if you're serving a public website does it make any difference?
"Own your data" maybe is not the right term. What is needed here is that your data does not vanish because the hosting service goes down or under or terminates your account.
Maybe things like Mediagoblin or IPFS could do that job.