Is Bond Portfolio Rebalancing Optional? Contradictory Info

Hello, I noticed that SS.13 has the LOS d. “Demonstrate the use of equity & bond futures to adjust the allocation of a portfolio between equity & debt” This is covered in calculations on p.115 (Exhibit 7). But the section explaining the formulas is pp.81-97, which is marked as optional. So is it optional or not? If it isn’t, then pp.81-97 should NOT be optional. Latest errata does not cover this at all.