What is the difference between diopters sitting in front of the lens and diopters on the rear side of the lens?

“Diopters are traditionally positioned in front of a lens to reduce the minimum object distance (MOD). ARRI’s new Impression V Filters have a completely different purpose. Attached to the built-in rear magnetic filter adapter of Signature lenses they alter the aesthetic look of the lenses. Known as bokeh, these elements play a significant role in the emotional perception of images.”