Bot kills aren’t tracked. They will always show as zero even though the bots are definitely getting kills. I have no idea why the developers insisted on showing zero kills, though, because it reinforces the perception that these bots are useless.
Which isn’t true, by the way. The bots are weird. As near as I can tell, they’ve got cooldown timers that let them heal you or heck a grenade every now and then. But they’re effective in that they stay with you*, they’ll serve as willing ammo mules, they’ll revive you, and they’ll do their fair share of killing stuff. But the trade-off is that you’re opting out of the card play for each slot you fill with a bot. And the card play is the foundation for playing at harder difficulty levels.
In other words, as is the case with similar games, the bots are fine for getting you through the game at the easiest difficulty level. They’re a good way to explore the levels and especially to learn the effects of the corruption cards. But they’re never going to replicate how gratifying these games are with human players who are communicating with each other.
* This is what makes them more useful than the average rando human player.