As administrator of a JIRA instance
I would like to control who is allowed to transition issue statuses for Simplified workflow-based projects
so that people other than team members cannot transition issues, just as they cannot edit (or create) them.

Additional explanation:
Issue creation or editing is controlled by a specific permission while, to-date, issue transition can only be controlled using Transition Conditions at workflow level.
While this is feasible (yet time consuming) for custom workflows, it becomes difficult for Simplified Workflows, where conditions are added implicitly as we add statuses.

I would find fair that platform admins could control issue transitions, especially since even project admins cannot modify their own Simplified Workflow on this aspect