Foundation puts a meta tag into head like: ”small=0em&medium=40em&large=64em&xlarge=75em&xxlarge=90em";
It then reads those queries in util.mediaQuery.js and uses it to enable js breakpoints and other JS stuff.
The _init function of Foundation.MediaQuery does the following:
var extractedStyles = $(‘.foundation-mq’).css(‘font-family’);
The meta tag is empty at the time util.mediaQuery.js initializes.