Tailwind is a CSS framework and not HTML.

Tailwind and CSS have nothing to do with semantics of a document outline and its markup.

Tailwind is cramming CSS into HTML. It has everything to do with markup.

You are right. And I said the same thing. Tailwind is CSS but that has nothing to do with markup which is strictly HTML.

Markup is the description of the contents of the document. CSS is the styling of the document and has nothing to do with description of content. That is the realm of HTML.