Greetings from Syncfusion.
We have analyzed your query, we would like to inform you that DynamicResource feature only works for the object which is inherited from View and added in the visual tree. ChartTitle, DataMarkerLabelStyle, ChartAxisTitle are BindableObject and not a View, hence DynamicResource is not working for FontFamily property of ChartTitle. We have already logged a feature report for this.
We don’t have any immediate plans to implement this feature. At the planning stage for every release cycle, we review all open features. We will let you know when this feature is implemented.