I'm saying that "sideloading" a K8 file via emailing it to your Kindle address, or by using the "so-called" wifi transfer option available in the Explorer Window (send by wifi to Kindle), which is actually the emailing option, converts a K8 book using the Document Service, which produces a K7 book. Thus, if you had styling in CSS, you'd get an old-style MOBI, not a new-style MOBI.
This means that any font you embedded, won't be. Ergo, no font-variant, as there is no font.
That's why I was asking.