Question on Alternates and Additional Services

One of the questions in the practice exam reads:
"Just prior to bidding, the architect and owner have some concerns about the price of the project. The owner asks the architect to provide a few alternates as options that might lower the overall cost.

Which one of the following is true based on AIA document B101-2017?"

The correct answer is: “Designing and documenting the alternates would be included in the architect’s basic services” and the explanation reads “According to Section 6.3 of the AIA document B101-2017, which is the “Standard Form of Agreement between Owner and Architect,” the architect shall provide alternates as part of basic design services.” The specific section in B101 reads: "In preparing estimates of the Cost of Work, the Architect shall be permitted… to include design alternates as necessary to adjust the estimated Cost of the Work to meet the Owner’s budget.

I am a bit confused, because AIA B101 S4.2.1.6 lists “Preparation of design and documentation for alternate bid or proposal requests by the Owner;” as an additional service.

When are alternates considered a basic or an additional service?