The out of focus spots are an 'image' of the aperture mask. So they'll take on whatever shape the aperture has... not its physical shape, but its optical shape.
In an anamorphic lens the image is squeezed, so the effective aperture is squeezed... well, in most of them. There are anamorphic lenses with the anamorphic part behind the iris, and for those you don't get the oval shaped oof highlights.
