Getting shadows right is incredibly complicated. You need to figure out the silhouette of the object from the perspective of the light source, then project that silhouette over the geometry the shadow falls on, then draw the perspective of that projection from the point of view of the “camera”. So it is a perspective of a projection of a perspective. And to add to that, objects occlude each other, and you might have multiple light sources. Since most artists probably start with a composition in the 2d space of the artwork, there’s never really a coherent 3d space to place the light sources in or figure out those projections in. I don’t think you should expect anyone to get it right in a complex scene unless they are drawing from reference.