As a sales person you have an option to sell whole course materials (access to all units in the course for the specific Learning Path) or parceled material (access to authorized units only).
SCENARIO:
Student has been sold the entire course content but has authorized /paid for delivery of 20 out of 42 units in the course. You have an option to give him an access to the units that were not authorized for delivery, by selecting "Show entire course content" under Student Materials Access.
In other cases, select "Show authorized content only"
If you granted student an access to the units that were not authorized for delivery, they will be able to look through all upcoming units (browse and preview content) in their Student materials Portal, and even take the Online Practice. See below snapshot that illustrates how unauthorized for delivery by accessible for content units are marked in Student Materials Portal.