Alliance Magic Combat Bureau's research shows that a spellcaster's magical talent is an indivisible whole. The three major types of spells are artificially divided post-hoc; those with magical talent can use all types of magic.
In simple terms, humans can only be divided into "those with magical talent" and "those without." There is no such case as someone possessing only a partial talent for magic.
For example, during tests, even if a subject only displayed talent for fire-type spells, while the other two types remained latent, after prolonged training, they could still learn to use sonic-type spells and acceleration-type spells.
Take Winters, for instance. Although his specialty is fire-type spells, he is equally capable of using acceleration-type and sonic-type spells. it's just that his progress in the latter two is slower, which is why he prefers to devote his time and energy to fire-type magic.
