You are right. On BBref, he has 3.1, 3.7, and 6 WAR seasons, an average of 4.3 WAR. If you start at 4.3 and decline to 2.3 in 2021, that's the same 16WAR you came up with. I have seen the many arguments on TD that WAR isn't a useful stat. However, it's pretty well established that WAR and the price per WAR in millions match up extremely close to the dollars and years of free agent contracts. Since that is the case, it seems very important to pay attention to and understand the WAR stat.