A tipped employee must receive at least the tipped minimum wage before considering tips, and the normal minimum wage after considering tips. The only adjustment an employer is allowed to make is to increase an employee's base wage if the base wage + tips is less than the normal minimum wage. In no case can the base wage be less than the tipped minimum wage.

The people delivering here are "contractors", not employees, so this doesn't actually apply to them; what Instacart is doing here is merely reprehensible, as opposed to illegal.