Currently there are 2 configuration settings in ULS for web fonts:
- You can select the font (including your default font) for navigation etc.
- You can select the font (including your default font) for content (if that's in a different language from the navigation)
You currently can't set the fonts for <span lang="xy">..</span> (both in navigation and content), ULS loads a web font and forces you to use it. There should be a third option to control whether a web font should be loaded and embeded, or whether the default font should be used.