We tend to duplicate the styles that we use as a base on for other styles in other dictionaries, as is the case with most of the buttons. What would apply to the instances that you would have in your project is the last added implicit one. In case you would like to modify the style of the RadButton in the general stand-alone state, you should add it after our dictionaries. The button is part of the Telerik.Windows.Controls.dll, so its style that is used as base resides originally in Telerik.Windows.Controls.xaml.
We have duplicated that style mainly for the cases in which its native resource dictionary is merged after the StaticResource references, since this might cause a XamlParseException. In the best case scenario, I would advice on creating and modifying a copy of the style and merging it after all the other dictionaries, so it would apply implicitly on any standalone instances, but preserve other occurrences in our controls that rely on our default style.
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