Owner permissions of the community/personal sheets are not re-assigned after the app has been restored/imported. See this article: https://community.qlik.com/t5/Knowledge-Base/How-to-backup-migrate-move-re-import-community-and-pers...
Imagine, having a hundred of community/personal sheets on the app, and for any reasons, app is delete or something else. If I restore it by this way, it will be completely a mess (all sheets will be in baseline).
Ideally owner permissions of the community/personal sheets should be re-assigned after the app has been restored/imported.