Okay, so looking at your page source an awful lot of Google Fonts are loaded — even when they’re not actually used in the frontend.
This is line 118 – 135 from the page source of your homepage, and I removed all lines pointing to your staging site’s URL:
<link rel='stylesheet' id='vcv:assets:source:styles:httpsfontsgoogleapiscomcssfamilyopen-sans700regularsubsetcyrilliccyrillic-extgreekgreek-extlatinlatin-extvietnamese-css' type='text/css' media='all' />
<link rel='stylesheet' id='vcv:assets:source:styles:httpsfontsgoogleapiscomcssfamilyopen-sansregularsubsetcyrilliccyrillic-extgreekgreek-extlatinlatin-extvietnamese-css' type='text/css' media='all' />
<link rel='stylesheet' id='vcv:assets:source:styles:httpsfontsgoogleapiscomcssfamilyopen-sans700subsetcyrilliccyrillic-extgreekgreek-extlatinlatin-extvietnamese-css' type='text/css' media='all' />
<link rel='stylesheet' id='vcv:assets:source:styles:httpsfontsgoogleapiscomcssfamilyoswald700300subsetcyrilliccyrillic-extlatinlatin-extvietnamese-css' type='text/css' media='all' />
<link rel='stylesheet' id='vcv:assets:source:styles:httpsfontsgoogleapiscomcssfamilyoswald600300subsetcyrilliccyrillic-extlatinlatin-extvietnamese-css' type='text/css' media='all' />
<link rel='stylesheet' id='vcv:assets:source:styles:httpsfontsgoogleapiscomcssfamilyopen-sans300subsetcyrilliccyrillic-extgreekgreek-exthebrewlatinlatin-extvietnamese-css' type='text/css' media='all' />
<link rel='stylesheet' id='vcv:assets:source:styles:httpsfontsgoogleapiscomcssfamilyoswald700subsetcyrilliccyrillic-extlatinlatin-extvietnamese-css' type='text/css' media='all' />
<link rel='stylesheet' id='vcv:assets:source:styles:httpsfontsgoogleapiscomcssfamilyopen-sans300subsetcyrilliccyrillic-extgreekgreek-extlatinlatin-extvietnamese-css' type='text/css' media='all' />
<link rel='stylesheet' id='vcv:assets:source:styles:httpsfontsgoogleapiscomcssfamilyoswald600subsetcyrilliccyrillic-extlatinlatin-extvietnamese-css' type='text/css' media='all' />
<link rel='stylesheet' id='vcv:assets:source:styles:httpsfontsgoogleapiscomcssfamilyopen-sansregularsubsetcyrilliccyrillic-extgreekgreek-exthebrewlatinlatin-extvietnamese-css' type='text/css' media='all' />
So, the answer to your question is simple: OMGF is detecting all these fonts, because they’re loaded. You can use OMGF to clean up the unused fonts, by leveraging the Unload option.