Please see the attached screenshot. The font specified in CSS is Helvetica, but WebView uses Times New Roman to render the output text. The screenshot shows the same page rendered on the device webview and it uses the right font. The screenshot also shows the same text in Helvetica and Times New Roman in a Text Editor on the same machine.
The underlying CSS files is loaded through the HTML that is being rendered here, it is not applied to the underlying JavaFx Scene component directly