In addition to what CDP1802 said all UI controls in WPF is a new composition model. Every control is composed of one or more ‘visuals’. These visual sub-elements are turned into a hierarchical Visual Tree by WPF and eventually rendered by the GPU.
So its the rendering process which is done by a GPU. Generally GPU's are not x86 and x64 based and the data binding code is the IL code which needs to be processed by CLR and because its not related to UI its processed by CPU.
You can see the
documentation to check
Graphics Rendering Tiers in WPF
Thanks,
Hemant