Layout component rendering is duplicated

Using the documentDriven of @nuxt/content, but I found that the layout component rendering is duplicated https://stackblitz.com/edit/github-5hgwqx?file=layouts%2Fcustom.vue,content%2Fabout.md,nuxt.config.ts,content%2Findex.md

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Content Hello World Example - StackBlitz

Run official live example code for Content Hello World, created by Nuxt on StackBlitz