Report Access, Row Level Security, Report Owner etc.

I have one of the new App Workspacess, and have added new users to it with "Member" permissions.

However when you look at the "Manage Permissions" on the Dataset, all the users have current access = "Owner".
There doesnt appear to be a way to change this.

The knock on effect of this is that I have Row Level Security which is being ignored I think because the users are "Owner".