I don't think there is a good term in the context of the Internet. Or offline for that matter. Even if you printed your blog and handed it out on street corners, for it to be "fully owned" would that mean you make your own ink and paper?
But, I think using the term "fully-owned" to refer to pushing up to GitHub, then deploying to Cloudflare Pages is definitely not "fully-owned"
You're right that hosting on GitHub and Cloudflare isn't infrastructure ownership. I should’ve been more precise with the wording.
The OP's fully owned is analogous to someone else doing the printing for the privelege of spying on your readers.