Hello,
Accepting stories into the backlog is a business decision that is why it is restricted to Product Owners. By the way, the PO can also use the lasso to select multiple stories. Someone who is not PO cannot accept them whatsoever, even by drag’n drop. Here is the documentation for the roles: https://www.icescrum.com/documentation/roles-teams-projects/#roles
PO is not just a « label » chosen randomly as you suggest, it’s access control, a thing that you will find in almost any advanced application.
We chose to offer a restricted number of roles that embody the main distinct responsibilities that you can find in an agile project: team organization (SM), business decisions (PO), work (team members).
We prefer this approach to a fine-grained permission control that ressembles micro-management and that would be contrary to the assumption that team members are collectively responsible for their fate and should trust each other (which is essential for the project to succeeds).
This assumption is also why we offer a role with full permissions: PO&SM, which you may use in your small team where the distinction between roles is apparently not relevant.
While we cannot get rid of access control entirely, this offers the best of the two worlds: truly agile teams can forget about permissions and grand everybody the PO&SM role, other teams can still get relevant restrictions/permissions with the other roles.