E Pluribus Unum is one of the US mottos... the original one, in fact. It was not to my knowledge ever engraved on our coins, but has been and still is printed on our paper bills as part of the image of our national seal.
E Pluribus Unum is on all of our coins. You just have to look for it.
Did some research and found that, in addition to appearing on the obverse (back) side of the One Dollar bill, it has been engraved on our coinage for a while:
https://en.wikipedia.org/wiki/E_pluribus_unum
Furthermore, according to the link, while it was:
“Never codified by law, E Pluribus Unum was considered a de facto motto of the United States until 1956 when the United States Congress passed an act (H. J. Resolution 396), adopting “In God we trust” as the official motto.
So, while the college president mistakenly called E Pluribus Unum the national motto, author of the critical post is also omitting an essential bit of information as E Pluribus Unum was unofficially one of the mottos of the United States from its appearance on the Great Seal of the United States in 1782 until officially superseded in 1956.
https://en.wikipedia.org/wiki/Great_Seal_of_the_United_States