[Gameplay] True damage and Dragons (Maybe bug?)

I'm a not a frequent on the forums, but I just noticed something while testing numbers recently. As we all know, True damage should not be reduced by anything, as has been the case forever now. I've noticed that while stacking Dragons, that the true damage being dealt was actually reduced. You'll see in the video I posted that while the dummy took full true damage, the Dragon's damage was reduced by 21%, as I killed 3 dragons to maximize AD.

I can't imagine this is intended, as Baron takes full True Damage.