It’s too much beating around the bush!
When you cross your legs, it will lessen your mental outflows. As a result, your head is clearer. It thus enables you to be more productive.
For example, when sitting in front of your computer, on your sofa in front of the television, at your drafting table, etc., crossing your legs will help make you more productive mentally as well as increase your stamina.
Therefore, sitting in full lotus can sharpen your focus and speed up the mental processing of your conscious mind.
On the other hand, when we sit in full lotus to do Chan meditation, our objective is to become single-minded. As we become more skilled, we can still our conscious mind.