What drives skin deformations in Unreal CPU or GPU?

Hey guys,

So my question is what is the main driving force behind the calculation of mesh deformation in Unreal? Is it the CPU or GPU? I understand that GPU will be displaying the triangles or tesselations etc… I also understand that Moprh targets can be either GPU or CPU with the latest releases, and that Apex is pure CPU. So what about the actual skin deformation calculations, is this handled by the CPU as well?