When using a StyleGroup, the ParagraphStyles are not inherited from the base style.

[CraigSiemens]

Normally a style from the base style is inherited if a nested style doesn't override it. It seems like every field in NSParagraphStyle is overridden if one field is set on the paragraph style.

let baseStyle = Style {
    $0.lineHeightMultiple = 0.9
})

let headerStyle = Style {
    $0.paragraphSpacingAfter = 16
})

let style = StyleGroup(base: baseStyle, ["header": headerStyle])

This will cause the header text to no longer have the custom lineHeightMultiple applied to it.