I’ve heard something similar for market research. Executives are generally far too busy to have their finger on the pulse of anything except their local corporate community, and so hire companies which tell them what trends and ideas are popular. And unsurprisingly, these companies mostly source their information from Twitter and Reddit, without much concern that these places are sort of cesspools.
The result, as expected, is unintentionally extremist views (in the literal sense, views from the tail end of the bell curve no matter the subject matter, and not necessarily related to politics whatsoever) propagate even further.
For video models, the data mostly comes from YouTube according to the article. However, YouTube now has an option to disable training on 3rd party models, which I've already done. Unfortunately, you can't disable it on first-party training (i.e. Google).