This post has no block delimiters. Not one. It is the way WordPress content looked for fifteen years, and it is still how a large share of the web’s WordPress content is stored today.
Paragraphs here are separated by nothing more than a blank line. WordPress runs wpautop() at render time and turns them into markup on the way out the door.
A migrator that walks the block tree finds an empty tree and reports, quite truthfully, that it converted the post successfully. The reader gets a blank page.
Inline HTML still works, because it always did. So does a link.
