In a way, that is not surprising at all. There are many things that never see the light of day. Whether or not it happened as JohnnyE stated, we probably will never know. So, at this point it is pure conjecture.
Does that mean Castro doesn't have some questionable activities in his past? Of course not! Anybody who is the sole authority under such a system is bound to have skeletons in the closet. Some we will find out over the years (if not already) and others we will never know about. That is a fascinating part of history...