All of these are supported in pandoc markdown:
> .mdv is strict CommonMark plus four additions:
> YAML front-matter for title, theme, named styles, and dataset references.
> Fenced blocks for data/visuals: ```chart type=bar x=region y=sales.
> ::: containers for styled regions and layout: ::: callout / ::: columns.
> ::: toc for an auto-generated table of contents.
Indeed. This is just a vibe-coded addition to an already overcrowded space, with no indication of any intent to consult others or support it for real use.