[Sophira]

In my experience, models do not tend to write their own HTML output. They tend to output something like Markdown, or a modified version of it, and they wouldn't be able to write their own HTML that the browser would parse as such.

[BugsJustFindMe]

What, in your view, does sending one markup language instead of another markup language tell you about whether the back-end executed some code or only pretended to?

The front-end display is a representation of what the back-end sends it. Saying "but the back-end doesn't send HTML" is as meaningless as saying that about literally any other SPA website that builds its display from API requests that respond with JSON.