It isn't that difficult to appreciate. For a given field of view you need to use a shorter focal length lens (by a factor 2) on a m4/3 camera than on a full-frame camera to take the same picture from the same position. The results are typically viewed at the same size. Therefore you get a greater depth of field in the image taken with the smaller camera. Digital compacts (which had very, very small focal length lenses) waved bye-bye to the out-of-focus woes of the 35mm film compact they quickly replaced. Now I understand that image processing to "blur" backgrounds is built in to some cameras (e.g. phone cameras) to [optionally] be rid of their enormous depth of field.