To answer original question...... Bus needs 2Kt GS to register 'out'. So new tug driver under training can dely your 'off blox' by pushing too slow!
Great trick about reapplying park brake just before door open though. Will do that evry time we have to wait for staff.
Other gotcha is if Cabin crew reclose door for some reason like repos jet bridge then that resets ACARS OOI data for next sector. Not very helpful if you now have to file log info manually.........
