From MoodleDocs

All users with this capability are considered as potential reviewers during the allocation. Submissions can be allocated to these users for assessment. Note that the lack of this permission does not mean that the user is not able to become a reviewer. For example, users with a capability to allocate submissions can assess any submission as they can allocate it to themselves.

This allows a user to

  • see instructions for assessment
  • train assessment process on example submissions