I looked at this a few years back with a 3270 screen. The big thing was, if you maintain a persistent connection, have a real terminal logged in and do the ops it can be faster. Their scrip had to authenticate then traverse sub menus, to get to the data. If you were logged in and ran thread safe calls to the terminal that ran the script then left a menu depth state or retuned to a root menu things would work better.
Another note, at least the IBM box I was on, each user was restricted to only log on one session. The SysOps had a higher session limit. A gui App you are used to making multiple calls. These would probably lock waiting for a clean session.