There is no clearly established formula for WAR. Sites that provide the statistic, such as Baseball Prospectus, Fangraphs, and Baseball Reference, all calculate it differently
First off, wins aren’t entirely linear. A player who is projected as a +2 win player won’t have the exact same impact on a 60 win roster that he would on a 95 win roster. There’s diminishing returns that start kicking in, and there are only so many at-bats and high leverage innings to go around.