The people making those claims probably believe that everything would break without JS, because they are looking at it from the perspective of a business or designer. If you consider your own site to be "broken" if the analytics/tracking doesn't work, or the fad "UX" effects are not rendered, they it's easy to believe that JS should be mandatory.
This point of view is based on a fundamental misunderstanding of what the web is. HTML is more concerned with semantic abstractions than the specifics of how a page renders (use a pdf if you want to control the layout). This was an important design choice because it recognizes that the client is responsible for the rendering, which is free to completely ignore the suggestions made by the page.
Unfortunately, far too many people don't want to accept that they don't actually have control over the browser.