Harvey Haddix' famous game

[greymule]

Most baseball fans know that Harvey Haddix of the Pirates once pitched 12 innings of perfect baseball against the Braves, only to lose in the 13th (May 26, 1959). However, the game ended on a strange play, and I'm trying to figure out why the league ruled the way it did.

Felix Mantilla led off the bottom of the 13th by reaching on an error by Don Hoak (though apparently Rocky Nelson missed a routine scoop at 1B). The next batter sacrificed Mantilla to 2B, and Hank Aaron was walked intentionally. Then Joe Adcock hit a liner that just barely cleared the outfield fence. Aaron, thinking the ball to be in play, stopped running between 2B and 3B when he saw Mantilla score the winning run. Aaron then started toward the dugout and was called out for abandoning his effort. Adcock finished running around the bases, and everyone left the field with the final score 2-0.

However, upon reviewing the play, NL president Warren Giles ruled that Adcock should have been called out for passing Aaron between 2B and 3B. So Adcock was credited only with a double, and the official score was changed to 1-0.

But Adcock passed Aaron only because Aaron had abandoned his effort (and was called out for doing so). If Aaron was out, how could Adcock be out for passing him on the basepaths?

Does anyone know the answer to this?