I am not sure from where you took the rules, but the last discussion was about a slightly different set of rules that keep both the hamburger icon AND add the text so that both younger generation and older ones can understand
.is-mobile .genericon-wvrx-menu:after
{content:”MENU”;font-size:90%; padding-left:10px;vertical-align:top;}
.is-mobile .menu-toggle-button {width:5em;}