The Mercedes-Benz W221 is a chassis code of S-Class, the successor of the Mercedes-Benz S-Class (W220) and the predecessor of the Mercedes-Benz S-Class (W222). The S-Class are the flagship vehicles of Mercedes-Benz and each generation typically introduces a range of technical innovations and developments that over time will find their way into smaller cars.
The W221 is the last S-Class vehicle made by Mercedes-Benz.
The statement is definitely incorrect because the excerpt states that the W221 was followed by the W222, which means that the 221 can't be the last S-class model. The system may have struggled with the wording in the excerpt.