Learning data will now be captured and frozen as a 'snapshot' of a User's progress status, once Unassigned or Deactivated. Content can be changed but their data will remain the same, until reset upon being Reassigned or Reactivated.
Frozen data allows for accurate reporting at all times. Recalculations mean that even with content settings and requirements updated, the User's progress will be re-aligned to match them.
To understand more, read the following support article: Understanding how insights are Frozen.