Applicable only for BigCommerce API v3 connections. If set to True, this field returns a JSON array, containing information about custom fields and their values for products, if such are available. Otherwise, it always returns null values.
This parameter does not affect working with custom fields for customers and customer addresses, and it also does not affect access to product custom fields via the ProductCustomFields object.
Please note that processing custom fields may take an additional time and API calls, so it's recommended to set this parameter to True only if you need to work with product custom fields via this connection.