Im pretty sure he wasnt the leader in much last year. Also its early so one amazing match could have you near the top in aces. As for the percentages, well if you havent played much and served well in the games played, then the service % is high.
If you look at the AO stats on their website I think Fed was #1 in only one stat, but yet he walked away with the trophy. Stats are misleading, especially this early in the year.