I don’t think Irwin ever said that. He mostly said that wages are not income. Wages are an exchange of your time for money. There is no derived (calculation). The 16th amendment did not authorize taxing wages. which is truly does not as the wording suggests. Wages are authorized to be taxed directly without apportionment via the court case Glenshaw Glass. Which interpreted the word income to mean “any Appurtenance to wealth” additions of value thru no effort of yours. You borrow your friends car for free and put new tires on it. He has to pay income tax on the value of the car with new tires.
Irwin wrote books telling people not to pay income tax and he also refused to pay... this is why they kept him locked up for a very long time.