This is the point. You can post anywhere, it will help to grow and learn.
Because many who are experienced, don't always go to the beginners' tab. So if you have a mining question, go to the mining tab, and so on. In these places you will find what you need.
Your right, because newbies are not limited to post to any board, because going different location of the community for conversations will enable them to have versatile knowledge, even i could remember when i was a newbie, i devoted my time to read across the boards in order to understand the concept of the community fully, and when this happens i started earning merit, so in summary a new user are meant to penetrate to any board and acclimatize with their subjects so that when making a topic he/ her will know the exact board to Post it.