In my experience, a picture that you insert to replace an existing one, using Change Picture, will "inherit" the crop&size settings of the old picture IF the old&new images are actually of the same size (in pixels) - if not, the new one will revert to the default crop&size so you will have to redo these manually.
This changes if the image to-be-replaced has any crop setting applied to it in Powerpoint. In this case, the replacing image will not inherit those, and might also be inserted with a different size&position, leading most likely to an unwanted result & further work needed.
A workaround I found is to first remove the crop setting from the old picture, replace with new image, then reapply the crop. This is still less work than having to manually redo the size&position (or to define these based on numbers copied from the PropertiesPane of the old image).