Markdown formatting with YAML header

[fmichonneau]

In my settings, in the language section, I have:

"Markdown": {
      "format_on_save": "on",
      "soft_wrap": "preferred_line_length"
    }

When writing a pure Markdown file, these settings work just fine:

However, if the Markdown file has a YAML frontmatter, Zed doesn't seem to detect that the content is in Markdown and the formatting does not get applied:

are there any additional settings that need to enabled?