Graves dealing true damage when attacking.

So I just played a game against a graves who dealt true damage with his basic attack, about 100 every auto, I managed to get this one screenshot luckily would have had another one where he dealt 360 true damage on about 2 autos but I wasn't fast enough to get one it as I opened the death recap when I had only a few seconds left before I respawned and saw that. No idea why it was happening but, you know, spaghetti code strikes again... Might just be the death recap, but I'm pretty sure he was actually dealing true damage on autoattacking. And I'm almost 99% sure it wasn't redbuff, didn't see him have one and if it was, the damage would be added to the basic attacks in the death recap. Also the description of the damage source was: gravespassive (Insert the players name here).