Comment: The distinction is with direct vs. indirect.

It's really that simple. The sixteenth amendment does not deal with the two types of tax clearly defined by the constitution.

"The Congress shall have power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several states, and without regard to any census or enumeration."

The two Constitutional requirements for taxes are:

Indirect (excise, duty, imposts), must be geographically uniform.

Direct (capitation, property) must be apportioned among the States.

Clearly, the "income tax" is unapportioned and therefore must be an indirect tax. Indirect means a tax on activities, events, incidents or occasions. All of which can be avoided and have nothing to do with income.

Again, the 16th amendment does not define a class of tax, therefore the original Constitution MUST be used for clarification as the Supreme Court has ruled.