It's very hard to capture this because it doesn't happen too often but I've uploaded a video where it shows part of what I'm talking about.
The video shows that I down 2 players. Because I don't quit when me and my squad are killed you will see it shows eliminated twice on the screen for the players that I downed after the player who kills me then kills their remaining player (who was trying to revive his teammate at the time). BUT I don't get kill credit and neither does the player I am watching. The player I am watching only gets kill credit for the remaining player he kills. So that means nobody gets kill credit for the players I downed.
If you see I had 2 kills before I downed the 2 players in the video and at the very end of the video it shows I still had 2 kills.
Now if I had stopped watching after I was killed and I quit the game and if the player killed the already downed players first he would have got kill credit for both of them but if I was still watching it would say eliminated on the screen (as though I had killed them) and nobody would get kill credit.
I will try get another video to show more of this theory if I can.
Ignore the poor gameplay, I'm not that good at this game.
https://youtu.be/adMo482Mk78