Unable to specify font-size in a way that respects Windows 10 text scaling

This is related to the accessibility feature of [increased text size ](https://support.microsoft.com/en-us/windows/change-the-size-of-text-in-windows-10-1d5830c3-eee3-8eaa-836b-abcc37d99b9a)in Windows 10 and is completely unrelated to the display DPI.

Basically: Is there any documentation on this? If I don't specify any font size my text is automatically adjusted (For example in a ``)

There seems to be no way to specify a font size in WPF relative to this base/system font size? Or the documentation for this very hard to find.