Kalista and her pet dog, Doesn't work as expected [Bug/Tool tip needs an update]

Why doesn't Nasus get stacks when he last hits with Kalista's Sentinel passive?

So my friend and I had the great idea to play Kalista and Nasus bot lane, where Nasus could stack q but Kalista would get the gold due to her w passive. It was great fun, good theme, decent late game and a good trade off as Nasus cant really contend early with normal supports. But then we realised that Nasus would only get stacks with relic charges and not the passive from Sentinel.

Looking into the ability i find that the tool tip doesn't reflect the functionality in that it doesn't mention that if the Oathsworn kills a minion with the attack, Kalista receives the gold for it. Theses minion kills also count toward Cull's passive. I've linked the champion page on the main site and there is no mention of this interaction, only the damage is mentioned.

Please change the interaction to be coded like relic stacks so Nasus can get Q stacks, or at the very least update the tool tip to reflect the actual functionality of the ability.