[SquareWheel]

If I understand your question, you're asking about adding functionality to a webapp to make it feel like a webpage rather than enhancing a page to add new features. The best two examples are actually mentioned above.

1. Using history.pushstate to intelligently add to page history for meaningful changes to the page. This ensures pressing "back" in your browser is still reliable.

2. Using server-side rendering on the first render. This keeps SPAs fast while the payload is being transferred.

Regarding Wikipedia's definition, that's a more broad definition than I'm used to seeing (speaking as a web developer). I've always heard it in reference to falling back gracefully from Javascript - usually with a <noscript> tag.

Supporting mobile, weaker networks, accessibility, etc. fall into much larger categories. Many of these topics require their own discussion and best practices.

Those topics are of course still important today (if not even more so).