Does anyone agree with that statement?
Sounds about right! Graphic design is lots of dealing with fonts, logos, product packaging, print layout, etc…
What would be the purpose of getting certified? Are you looking to pick up freelance work? If so, it would be a lot more helpful to build up a specific portfolio for the type of work you want to do (e.g. a portfolio of just logo design if you want to design logos, just illustrations if you want to do illustration, etc…).