By adding an extension between the camera and the lens, in this case a converter so I can use EF lenses on my Canon M50, you would think any lens would focus closer but it doesn't. Why is that? :/
EF lenses are made with a 44mm registration distance. That is, the flange on the back of the lens is intended to be 44 mm in front of the imaging sensor or film. This allows the lens to focus the light striking the front of the lens on the imaging sensor or film that is 44mm behind the flange ring on the back of the lens.
EF-M cameras are designed with an 18mm registration distance. That is, the flange on the back of the lens is intended to be 18mm in front of the imaging sensor or film.
An EF to EF-M convertor adds the other 26mm needed to place the flange of an EF lens 44mm in front of the imaging sensor on an EOS M camera.
Without the convertor that extends the camera's 18mm flange distance, an EF lens would be focused 26mm behind the imaging sensor. The lens would be "focused" well past infinity and nothing would be in focus.