That's true for the Total Science score, but the Academic Average is the "composite score representing the average of qr, rc, phys, bio, gchem, and ochem standard scores" [abbreviations are mine]. That's probably why the TS score is used for entering class stats; it's a better representation of how candidates preformed v. their peers.
I don't know if they round the AA up, but they definitely rounded mine down
- polkadot.