3
Yes and no.
xoopsTree is part of the XOOPS code library. and its has 100% support for category/breadcrumbs... so any module can utilize this feature. Alot do such as WF-Downloads, etc...
Its just that XOOPS core itself does not make use of the XoopsTree class too much, so thats why there are no breadcrumbs by default.
That is, if every module you used supported xoopsTree, then you would get the result most people are looking for with using breadcrumbs.
But alot of modules do not need categories (xoopsTree) so the breadrumb sipport accross the site is sporadic. The modules that need it do support breadcrumbs.
Nothing wrong with it either. It makes for a very flexible system.
XOOPS Rocks.