I've tested it on a dummy epub (2 html files, one paragraph in each, one referencing embedded font one not) created using Calibre Editor and for that epub file plugin works correctly, it copied .ttf file(s). But it's not working for my copy of
The Malazan Book of the Dead omnibus 1-10, probably because of non standard internal directories inside of epub...
When you said "you can use Polish to remove unused fonts" were you referring to Calibre's "Polish Books" toolbar button? Because I don't see options for removing unused fonts (files, not CSS), just for embedding referenced fonts and subset-ing embedded fonts.
I'm just wandering if I'm missing out on some Calibre functionality...
I'm used to checking every book in Calibre Editor and while checking/editing CSS I always check if the book contains unwanted fonts (most often deleting Charis SIL font files
)