Original: If a wiki has a passing need for an edit to be oversighted, for instance, a steward can add themselves to the 'oversight' user group on that wiki, perform the necessary oversight activity using Special:HideRevision, and then remove themselves from the 'oversight' group using their steward rights.
Simplified: If a developer needs access to a specific permission on wikipedia, they can assign the permission to the 'developer' group, then add themselves to the group using steward rights.