This seems to be quite a trap, as the documentation (XDMF Model and Format - XdmfWeb) says the values are x,y,z - but apparently they are swapped in the reader, for example: VTK/IO/Xdmf2/vtkXdmfReaderInternal.cxx at ff6e52da50e3b29f5c18de6d7a9e14d39548c8bb · Kitware/VTK · GitHub
Is that just an error in the documentation?