Dunno you didn't say if this was suppose to be realistic or based on game logic where mothers send children off at ten and famous Red catches all pokemon and becomes champ xD

Well he does study pokemon and he wasn't actively searching for legendaries. Only searching for his sister in which him and the Latios share the same goal while being in the police force and battling against pokemon stealing corporations. It did just happen to be luck and share a common goal. 

So if it bothers you that much for it I'll put a non legendary as replacement xD now to just decide on which.