No this is really likely, the items really are handled as a “drop”, they’re generated when the zombie dies. I think there might be an override that gets set when a necromancer raises a zombie, and we forgot to set it when we have a zombie self-rez.
What I really want to do is have the stuff appear on spawn, and you can see what the zombie is wearing ahead of time. This requires re-working how persistent zombies are handled, right now if you leave the area and come back, you get a whole new set of zombies, but they’re the same type as the previous ones and in the same locations. To do what I want we’d have to save the actual zombie so HP, conditions, items would also be persistent.