There is a discussion about this and a plan to change/fix it. Not sure if it has been "approved" yet.
Others that have seen the process, please chime in, but my understanding is that typically your selects rack and stack higher in the DT. When designating a guy to a particular school, typically the higher on the list you are the "better" the school you go to. Additionally, you'll see HPOs go to a school that may result in joint duty on the back end to get their JSO designation, etc. If already joint complete then you may see the HPOs go to an outside the AF school. YMMV.