[rualca]

> I would rather have my files be Page.component, Header.component, Details.component, Article.component than have my three files be Page.html, Page.css, Page.js.

...except that Page.css at most only adds minor tweaks that cascade over the site's styling, and arguably already should be a part of the site's main styling definitions.

> What is the benefit of separating code by file type?

Separation of concerns. This lesson was learned the hard way. Must we keep on relearning it?

> I think this is false simplification - again, in complex applications with lots of interaction, there is no escaping the coupling of DOM nodes, JS logic, and styles.

This assertion is quite wrong and misguided. Styling is a property of a site's visual identity. It is not a property of a component or a specific interaction state. Any well-designed site follows a uniform visual identity which spans over all aspects pertaining to user interactions. Moreover, UI components are also uniform and reused. There is no excuse.