That's a pretty close description of how tipped occupations are handled.
According to tax law, tips are part of your income for both income tax and FICA purposes.
The IRS has a good idea of how much tipped staff receive, they have charts and schedules that tell them by percentage, and if you and your employer aren't reporting enough tips received, they will require the employer to presume you received them anyway. That's why the employer has to track the tips, add them in and then subtract them back out.

