The lawsuit worthy aspect is that labels for buttons are super important for understanding what a button does. A lack of labels (either through not putting text inside the <button> element or using a technique like aria-label) can quickly make an interface unusable for a blind person - the visual equivalent would be completely blank, identical buttons. That barrier is what someone could sue over.

It can also quickly make an interface unusable for a non-blind person, if they block external fonts.