Since this presupposes Markdown of the flavor that comes with YAML frontmatter, and that frontmatter is doing all of the heavy lifting, this is more like a YAML database than a "Markdown database".

In any case, nowhere is it indicated why this approach (no matter what you call it) should be preferred over e.g. recfiles.

Yes it is markdown plus frontmatter that makes this work.

Point on comparison with other formats is really well taken. I think the main argument i would have is ubiquity of markdown and markdown tooling.

Or just embed structured data in any text file document, not limited to Markdown.

https://ddot.it

Disclaimer: My project