[GAMEPLAY] Vi's can still hit target if she ults to Kalista's ulted target

I was in a game today where I was Vi and I ulted the enemy Sona. The enemy Kalista absorbed the Sona, and I chased down the Sona until I reached Kalista (where the Sona was pulled into) and dunked the Sona. I was still able to autoattack the Sona after I ulted, even though she should have been invulnerable inside Kalista.

1. Make a game with Vi on one team and Kalista and Sona on the other team
2. Get Vi and Kalista to level 6+, with Kalista level 6+ bound to Sona
3. Go near the SW Red buff, and place the Sona between the top Raptor Wall and Dragon Wall (not in bush); Place Kalista in the bush on the backside of Red's wall near Dragon; Vi places a ward in Kalista's bush; Place Vi in the bush next to Raptors
4. Have Vi ult onto Sona, walking forward until she is in range
5. Have Kalista ult Sona so that Sona is absorbed into Kalista

Expected Result: Vi chases down Sona to the same spot that Kalista is at. Vi is able to keep autoattacking Sona.