Replying from the DFHack thread:
In short, I can access the information of some dwarves who are not residents in my fort by selecting (v)iew in some citizens' relationships screen. (snip)
I thought you were referring to the longstanding vanilla quirk where dead dwarves' information can be accessed in this way. Upon reading this thread, that's not the case. At any rate, I'm fairly certain this isn't
due to DFHack, although we can use DFHack to diagnose it somewhat.
Just to confirm, by "not actually citizens", you mean they're not visible
at all in any unit list besides relationships (i.e. they're not listed under 'u'), right?
The zooming behavior is strange. What do you see in the DFHack console if you run ":lua ~unit.pos" with one of these units selected in the relationship list?
Was this save created in 0.44.12 or an earlier version? Run "devel/save-version" just to be sure.
Might be just your zoom is broken
This behavior is actually fairly typical for off-map objects. An "invalid" position is usually represented as (-30000,-30000,-30000), which DF thankfully adjusts to (0,0,0) when zooming to it, and that's the location being described here (bottom z-level, top left).
I am curious why you jumped to this being a DFHack issue, though - have you seen something like this that's DFHack-related? There hasn't been much research done for the new stuff in 0.44.12 (besides necessary stuff like added professions), so it's not possible for any (official) DFHack tools to be messing with it directly (indirectly is admittedly another matter).