That quote is specifically referring to how much income tax an employer withholds from a commission based employee, not the actual tax rate the employee pays when preparing their income tax return.

Prepare the return like any other return - If the commission is on a W-2 just enter it like any W-2 based income.

If on a 1099-NEC - (Most of the time) they are treated as a proprietorship and the Commission and any expenses are reported on Schedule C.