I see what you mean now, I've logged this as an issue to fix, thank you <3 Good catch, good dedication.
Monsters not on the same floor should certainly stand still. Where did you notice this to not be the case?
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Do you recall what version the throwing items was from? I remember form tibia v6 you could do this, and you could also do this to shoot runes way off screen, but I don't recall in v7 or 7.4?
I will test this out on my real tibia server though to compare, thank you <3