Once the time period passes for a specific ban then waiver for that ban no longer needed. INA 212 is explicitly clear about that.
The reason the lawyer said that is in case the CO determines that a different ban also applies; for example, a misrepresentation ban. In that case, Form I-601 cannot be filed before the visa interview: https://www.uscis.gov/i-601-addresses "Seeking an immigrant visa or a nonimmigrant K or V visa and I have been found inadmissible by a consular officer after my visa interview."
