Kha'Zix passive bugged? dealing more damage than it should? secretly true damage?

I have no clue how to repeat it but this underfed kha did 1273 damage to me with 2 procs(I assume, looked like one) of his passive, but against almost 300 armor and 200 magic res, seems odd.

the match ended before I remembered to take a screen cap, but it said true damage yet was colored as magical dmg in death re-cap, maybe it's secretly dealing true damage?

anyway, I could be wrong but I think this might be similar to garens tricky bug where he did 1% of his own hp true damage instead of his targets.

just wonder if anyone else might have noticed it, if not keep an eye open.