It is possible to copy contents into a non container content, might be related to this issue EZP-23906. Can be seen on PlatformUI.

Steps to reproduce:

1. Go to PlatfornUI
2. Create some contents, one of them a non container
3. Copy a content into another one that is non container
4. The content is copied normally
5. Expected to see and error and a message informing that is not possible to copy to a non container