here it
Depending on how long it took you to win the 100 matches may be the cause of this. Some of the actual "requirements" aren't noted on the achievement page... such as time frame. Also, they often take a while to update. I remember waiting over a day (nearly two) for a full set achievement.
If it doesn't give you the achievement after a while I'll ask someone (Who will know/Can find out) about the more specific details.