Bug Rift Herald

So i just wanted to say that i found a bug that i saw in a live stream, so the "streamer" was playing master yi jungle with devourer and when he did rift herald he should get 2 stacks because of the new update but this was what hapend he got the assist not the kill and it buged and git him 5 stacks and not 2. BTW i just tested this in a normal gmae and it did the same thing i got 5 stacks because i got the assist.