Well, VP8 was only released as an open codec in 2010, and subject of patent lawsuits until late 2014.

In 2010 the majority of (YouTube and other) videos were still served as H.264, because no major browser supported it back then and the majority of video playback devices were already smartphones (without vp8 decoding capabilities)

iOS for example didn't support VP8 until iOS12 in 2019, Firefox and MS IE only added it in 2011. Even Google only added VP8 to Chrome in September 2010.

So the statement is correct IMO