I think important is, and that depends a bit about the role, that a full-stack dev can do everything needed in his role, related to development. So he can do so

I think important is, and that depends a bit about the role, that a full-stack dev can do everything needed in his role, related to development. So he can do some DB migration, if needed, he can do deployment without the need of a sysadmin. But a good Full Stack Dev has also to be specialist in eg Backend or Frontend. Just knowing a bit from everything after assisting 20 Udemy videos is not the point :-)