Aatrox passive kills undying targets?

IS IT INTENDEd for his passive to kill undying targets or is it a bug? I played in parctice tool, the practice enemy dummy has a min health of 100, where he can't go lower but aatrox actually manages to kill it with his max health passive. Im reporting this because is possible to affect tryndamere, zilean's ult, guardian angel and other undying things. i didnt test on champions, just on practice tool.
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