Moodle - Activity Completion Restriction not visible

There was a request for support, that on one of our Moodle instances, we do not see the 'Activity Completion' as an option in 'Restriction'.

From the documentation page,

https://docs.moodle.org/405/en/Restrict_access_settings

In Site administration > Plugins > Availability restrictions > Manage restrictions you can enable or disable (Hide/Show) any of the individual restriction types for use throughout the site. This was already enabled for the Moodle instance.

Maybe if you choose the first activity of a course, this option may not be available. Or if the activity is of type forum?

If I choose the second activity of this course, I see this as an option.

Another possibility for a newly created activity might be: 

it might need to be saved once before the condition appears, --or--

the completion condition might need to be added to the activity and saved before the condition appears, --or--
maybe you can save changes, log out and log in again and then it becomes visible.

Doing all of the above definitely seems to work.