A good coach will not use a INF as a P nor an OF as a INF. Nor would he put a C as an INF, nor as a P.
The throwing motions for each of those positions are different and require different mechanics.
The long-arm throwing motion, is not good for INF positions that use a short-arm, more efficient, throwing motion versus the C position that uses a quick-snap throwing motion. Those three throwing motions usually are not naturally acquired and are taught.
But in the case where you have a kid playing INF, P, and C it is important that they use the correct throwing motion for the position they play.