Actually they could do the same thing to any Fediverse link as they are with these news sites' links. They added a 5-second delay from when a twitter user clicks the external link from a twitter post, which is garbage overall, but not "throttling" websites. Yes I skimmed the article.

The headline seems to imply that Twitter controls the internet traffic to non-Twitter sites, which is misleading. Twitter is simply degrading the experience of their own site's userbase, and nobody else. The rest of us can still visit the news sites that Leon Skum hates without Twitter.