I could be wrong, but it seems like the article is saying that the core difference would be this:
React (rendering in the browser, not server side):
Page Load -> Component Load
vs.
Web Component
Page Load -> Default Render -> Component Load
So if someone has JS disabled they would still see SOMETHING for the web component vs. nothing in React. And with JS they could get to some further render state.
React (rendering in the browser, not server side): Page Load -> Component Load
vs.
Web Component Page Load -> Default Render -> Component Load
So if someone has JS disabled they would still see SOMETHING for the web component vs. nothing in React. And with JS they could get to some further render state.