You are likely sending the Appraiser a letter outlining your request. Make sure that the letter either:
(a) tells them they have a choice, or
(b) specifically labels VAL as a valid choice.
For example:
If the valuation of the property includes the Income Capitalization Approach (both direct cap and discounted cash flow analyses), you are [required/requested/encouraged] to utilize Rockport VAL. The VAL model and reports shall be provided using the Rockport VAL platform ‘Share’ feature.
Silence leads to misunderstanding.