Yes - when you create a connection from a shape's Connector the RadDiagram will create a RadDiagramConnection by default. To change this you'll have to inherit it and override the GetConnectionContainerForItemOverride method:
Note that when you create a connection from a connector we show it's actual geometry not the deferred one and because of this instead of UpdateDeferredGeometry CreateGeometry method will be called. Also if RouteConnections is true the FreeRouter will be used:
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