One for all bug?

I was playing one for all as lulu with a 5 man and had a point where I killed one of their Shens top 1v1 yet 2 people assisted, including me, and one person got the kill. Two people got kill participation, including actually getting the kill itself, while not even being remotely close. We suspected that it wasn't registering us as separate people. Just kinda weird and I thought I would point it out.