When deleting an image style, you are offered the option of replacing all uses of that style with a new one. We currently have no way to deploy this information, because when a piece of config is deleted, nothing is deployed along with it (its absence indicates the deletion.) We'll need to come up with something for this.
Top of the head thought: when an image style is deleted, we make a special config file with the replacement style info (if specified) aka image.style.large.replacement.yml or something. When config import runs, image_config_import_delete() can look for that file and handle it. This will leave behind an unused file on the source system unless manually removed.
Note this only relates to deploying deleted image styles with the configuration system. This still works in the UI as it did in Drupal 7, which is why it's not critical (this is a bug in CMI, not a regression from existing functionality.)