The @font-face rule is designed to allow lazy loading of fonts, fonts are only downloaded when needed for use within a document. A stylesheet can include @font-face rules for a library of fonts of which only a select set are used; user agents must only download those fonts that are referred to within the style rules applicable to a given page. User agents that download all fonts defined in @font-face rules without considering whether those fonts are in fact used within a page are considered non-conformant.
В общем, проверять загрузку шрифтов только через devtools, нигде не применив эти шрифты, было глупой идеей.