Completion and Progress are related but not identical concepts.
A participant becomes “Completed” when they have gone through all the mandatory activities. Moreover, completion never automatically regress to a previous state, so once a participant is Completed they will not switch to In Progress if, for example, an admin adds a new mandatory activity. Finally, Completion can be manually overridden by an administrator.
On the other hand, Progress represents the portion of completed activities over all the existing activities, regardless of the fact that they are mandatory or optional. Progress always updates automatically and can decrease. Lastly, an admin cannot update Progress directly; they can however influence it by marking activities as Completed.
Common scenarios where Completion and Progress can differ significantly:
The project has a meaningful proportion of optional activities
Participants has been marked as Completed manually by an administrator