What's wrong with aping a style you like? It helps you learn and figure out how the people who's stuff you like do the things they do. And since Santi's small catalog of posters here bounces around several styles, I'd say (he's?) still trying different things out until he finds something he can either make his own, or until what he's doing evolves into his own style. This is how almost every designer begins and learns, and many of us still wear our influences on our sleeves.