I'm a few years out of the game and don't have 5th books even, at this point, and trying to drag together again my mental map of the SR world.

Are the rules in 5th explicit about disallowing a meta human targeting a Sprite with an Aid Another action? If so is there any fluff rationale for it, and if not is there is any fluff rationale for why a GM might see fit to proscribe it?