It's supposed to learn Fire Blast at level 51, but a programmer made an error and accidentally had it learn Leer because their index numbers or whatever are right next to each other
Interestingly enough, despite them fixing some movesets from R/B/G to Yellow, they didn't fix Moltres in Yellow.
"Well, maybe the Dirt Dragon should have thought about that before taking over the opera house." - Lord_Bob_Bree