It is the heading tags such as h1, h2, h3 that matters not the font size as you call.
Websites are not ranked based on Font or text size, they are based on tags. If they were based on such font size criteria, can’t we all do the same for ranking purpose?
If SEJ is using large font size, it is because of the usability. Better user experience will help you to lower your bounce rate and hence help your SEO.