Body Scan Versus Feeling Breath Overall

Upon reading this post , I realized I always focused on the tip of the nose rather than the whole body, which may be less effective (for me). I was reminded of my Buddhist college teacher who said that meditation upon the body may cause psychosis or a mental breakdown for some. Hence, I wonder: **Is there any difference between mindfulness of the body (e.g. body scan) and focusing on the breath as it arises all across the body?** My teacher specified he believed focusing on the tip of the nose would avoid any such problems. **Is meditation on the breath as it arises across the body a variant or even partial form of body meditation?** Thank you