Class 2 Officials for Playoffs

Just saw the Pre-season Bulletin and had a question about the use of Class 2 officials for playoffs. Does this mean Class 2 officials will be used when all eligible Class 1 officials have been assigned? Or does this mean that eligible Class 1 officials can be passed over for playoff assignments by lesser qualified Class 2 officials?

I only ask because it does not seem fair to use less qualified Class 2 officials when there are qualified Class 1 officials who do not get a chance for playoff assignments.

Just the first 2 rounds if they have been part of the crew all season.