I can see an issue with that, which depends very much on why those activities are restricted.
In your use case where they are restricted based on completion of a previous activity what you say makes sense. However, if they are restricted because of, for example, group membership - used to (possibly) split groups so Group A does one activity, Group B another, or having a different submission date, then showing the total activities would not be appropriate and showing the activities available to that user is.
In your use case where they are restricted based on completion of a previous activity what you say makes sense. However, if they are restricted because of, for example, group membership - used to (possibly) split groups so Group A does one activity, Group B another, or having a different submission date, then showing the total activities would not be appropriate and showing the activities available to that user is.