Your auditor is correct if the grant has the following elements:
1. The grant is a unrestricted (i.e. without donor restrictions)
2. There are no conditions that have to first be met in order to receive the grant
3. The grant is not an expense reimbursement grant
If everything above applies then you record 1/3 of the grant in the current year as “Without Donor Restrictions” (i.e. unrestricted) and record 2/3 of the grant in the current year as “With Donor Restrictions” (i.e. temporarily restricted).