I looked at this yesterday and I see exactly what you are seeing. The dimension line terminations cannot be controlled at the instance level so they all have to be the same.
One workaround would be to change the Global parameters to bullet, clip out the leader dimensions that require bullets (File > Export > Sub-drawing), remove the leaders dimensions with bullets, clip back in (File > Import > Sub-Drawing) then change the Global parameters back to arrow. The clipped in leaders will be considered "old-style non-associated dimensions" so they will not change when updating the Global parameters for the dimensions. One note: You would still need to go into the Dimension Environment to delete these clipped in dimensions.
This looks to be an oversight/bug and should be addressed by Cadence.
Is there anyone else out there on a higher 16.5hotfix level that can check this to see if it acts the same way. (no control of terminations at the instance level)
I am running 16.5 S018.
Plexus Engineering Solutions