Difference between loading and expanding terms

I'm very interested in using taxonomy manager/tree widget for content taxonomy however I'm running into a huge performance issue. Even though taxonomy manager allows to either show entire tree or expand selected branch it always loads the entire tree when using content taxonomy tree on page load instead of loading only topmost level + selected term and its parents. Loading the entire tree might work for a small number of terms but causes a performance issue for large taxonomies.
In taxonomy_manager.module comments it is noted that it is possible to use pagers(#pager) instead of loading the entire tree (#render_whole_tree) however when switching to pagers default value is lost for the tree. Also are there any examples of taxonomy manager use other than content taxonomy tree out there?