I wouldn't say that it would be harmful to put your hand in the Akadema Prodigy Series: AOZ91-12 Youth glove, but it would alter how the glove is broken in. The problem would be that the glove would break-in forming to your hand rather than your players hand. It could also potentially stretch the wrist opening and finger stalls resulting in a more loose fit for your player.
Youth model gloves such as the Akadema Prodigy Series (AOZ91-12) will account for shorter fingers for players. For his age, we would typically recommend something a bit smaller possibly in a 10.5 inch size like the Akadema Rookie Series (AJP96).
Based on his age and position, we suggest an 11.50" model. The Akadema Prodigy Series (AOZ91-12) Youth is an 11.25" pattern and is an acceptable glove for him to use as well.