Today's schedule in Darwin for that service does actually have public timing and activity code "T " (stops to pick up and set down passengers) for HETNLJN...
<IP tpl="HETNLJN" act="T A " pta="08:47" ptd="08:48" wta="08:46:30" wtd="08:48:30" />
Our programming is the same and screens will show an untranslated TIPLOC if there is a public activity for a location with no associated crs in the reference data - there have been quite a few posts on here in the past of station and platform displays doing the same!
The "A " activity is "Stops or shunts for other trains to pass" which explains the working arrive / depart timing.