Devourer granting 1 stack on dragon (and probably baron) *assist*, rather than tooltip-stated 5

In two games, I got five stacks with the killing blow on dragon and one stack with only an assist. Both games were PvAI. One game was Warwick, another game was Jax. Both games were using Skirmisher's Sabre (challenging smite).

I observed someone else (Warwick, PvAI, Skirmisher's Sabre) getting only 1 stack on baron and dragon assists, but 5 stacks on dragon kill. This observation led to my testing.

Did not test different machete upgrades. Did not test interaction with the enemy team securing the kill. Did not test scuttler. Did not test baron.