A folder of Markdown files is a good source of truth only when the build knows what a valid file looks like.
This site gives each post a title, description, publication date, reading time, tags, and draft flag. The collection schema checks those fields before a page is generated.
One filter, every output
The same isPublished rule is used by the home page, post routes, topic pages, and RSS. That matters because a draft should not disappear from one listing and then leak through another feed.
A date in the future follows the same rule. It can live in the repository and be reviewed before publication, while the public build waits until the date has arrived.
Small rules compound
Typed frontmatter is not a replacement for editorial judgment. It is a guardrail that keeps routine mistakes out of production. The more outputs a site has, the more valuable one shared publishing rule becomes.