My take is Publisher (and/or supplied) font means:
1) Use the CSS or inline style= font instead of the devices choice (Just ignore everything the book calls for)
2) The font only needs to be on the device list of fonts for the PUBLISHER to use it. The device setting is still Publisher.
3) any of the tiniest CSS errors can get a CSS ignored. The wrong CaSe is a common one.
Windows is very lax, so the book may work there and nowhere else.
4) See the other posts
I do not allow 3rd parties to get between Calibre and my device (and tamper / adjust) so I only use USB