Kalista's damage from W passive no longer (patch 5.13) credited to Kalista but to her oathsworn

Let the ADC be Kalista Let her support and oathsworn be Thresh

When Kalista auto-attacks a minion and Thresh auto-attacks the same minion sooner than 2 seconds from the first attack the minion receives aditional damage that may execute the minion if he had 125 HP or less when attack by Thresh.

Now since Kalista's birth at LoL this extra damage was always credited to Kalista and not to the oathsworn, even when applied to enemy champions. However, since path 5.13 the damage is credited to the oathsworn who actually last hits the minions or the champion in question. This change was not included in the path 5.13 notes so I think it might be considered a bug with pretty important implications.

Now to reproduce the bug I'm positive it happens with Thresh as oathsworn but I have not tested it any further:

1. Pick Kalista
2. Pick Thresh
3. Make the oath
4. Go to lane and attack a minion until he is low enough
5. After the auto-attack from Kalista that lowers the minion to 125 HP or less make Thresh auto-attack it within the next 2 s
6. See the gold and the CS go for the Thresh while Kalista gets pissed: my farm pls

In this situation the bug happens just always meaning there's nothing special one must do to reproduce it.