Your attorney is conflating the following alternate valuation date for estate tax purposes with the step up in basis.
In the case of property distributed, sold, exchanged, or otherwise disposed of, within 6 months after the decedent’s death such property shall be valued as of the date of distribution, sale, exchange, or other disposition.
The best evidence of fair market value, and the only one the IRS must accept, is an appraisal by a certified real estate appraiser.
