The latter. It's a tailoring model and I wanted it to change automatically to match the race of the PC using it. That's really where I noticed that null-animation pose. It stays that way while in conversation and then animates when the conversation ends.
I find that this change of appearance breaks the VFX_DUR_FREEZE, and the re-application of it needs to be delayed 4+ seconds so you get a few seconds of hand movement and head wobble then you can re-freeze it. However, if I change the appearance back to default human after the conversation ends the appearance comes in as if spawned in sight (i.e. fully animated in ready pose). I can't get back to the null-animation pose.
If I don't change it back at the end it works pretty well. I can keep it in the null-animation pose all the time. I think this will work as long as I paint them down or be sure to spawn them when PCs are not around (I'll probably just do the former...).