learningContentRef / learningContentComponentRef

Hi

This may be a dumb question, and not the right forum, but does anyone know why "learningContentRef" and "learningContentComponentRef" have the same inheritance?

That is: " + map/topicref
 learningmap-d/learningContentRef " for both. 
If someone does know, could they tell me if this should be the case? And if so, could I have a bit of background?

Many thanks

Ian