There have been errors in other IRS publications (and instructions) over the years.
They are not authoritative but following them at least prohibits the IRS from assessing penalties and interest if they turn out to be wrong in some respect.
Your trade-in would be considered a sale since there are no more like-kind exchanges of personal property after tax reform (for the 2018-2025 tax years). Whether you have a taxable event depends upon what type of cost recovery you used (e.g., actual expenses with depreciation or standard mileage).