Some interesting facts in the article, however, saying a font is hard to read because it's too small is a bit of a loose statement. Font family, color, line-height and width (anything over 500px wide is a strain) all contribute to the readability of text. So a pink font at 16px stretching the full width of the screen (let's say 1400px) with default line-height might be easier to read if it were 13px, dark grey, 450px wide with 20px line-height.

The article doesn't target a specific type of site. Article sites or news sites rely on readability far more than startups. The article seems to suggest that you NEED copy to guide users. This statement is incorrect. You can guide users with whitespace, color, images, buttons, hover states etc.

If you have a startup landing page with lots of copy on it, regardless of font-size...you've already failed.