If you have a multiple heirarchy and you do not enable this option, the only breadcrumb displayed is 'home'. See the notes on multiple heirarchy menu ambiguity.
Taxonomy Treemnu tries to offer breadcrumbs when it can. If the menu term links are not derived from a multiple hierarchy, the menu shows a normal breadcrumb. This applies even if the nodes have multiple connections. But if you enable 'nodes' on the menu, then you will loose the breadcrumb.
Multiple breadcrumbs can be viewed with stock Drupal rendering. However, stock Drupal pages uses a fixed height for the breadcrumb area, and then absolute positioning to place the breadcrumbs above. For now, we have not adjusted this. To use this combination of options, the page must currently be altered so it will either have more vertical space, or take a flexible 'div' container at the top of the central container.
Taxonomy Treemenu's term-as-link renderer, will allocate appropriate space for multiple breadcrumbs.
See rendering multiple breadcrumbs to style multiple breadcrumbs for your site.