Yes could be a good Idea, but in this case the grant for the group 'Alle' was set deliberately since all the sites registered users (comming from Active Directory) are member of this group and they are supposed to be able to create workgroups by means of the Social group module.
When I look in the Core_Messages table it appears that these notifications at some point in the history of this website, that was build with Evoq/DNN 8 and has been though different configurations, were added to this table whenever a social group was created by a host/administrator user with these recipients: Administrators,Content Editors,Content Managers.