I just noticed that the guardian trait Renewed Justice (virtue of justice is renewed when you kill a foe) does not proc when you defeat a southsun settler (the ones that turn green when defeated instead of dying).
I don’t believe you get stacks with “on kill” sigils from these guys either.
of course, we’re not actually killing anyone, but these people do drop loot. So it seems different from other situations where foes turn green when defeated (for example with skill challenges).