As far as I know you need to manually enable KO for each creature, and then it's required. How I have it set up on my server is I have the "Enable Immersive Taming Only" option turned off so that players can tame immersively or through the normal methods. I have it so Immersive Taming is a little slower and is of course more work, but there are benefits to taming that way over the standard way, in my case, XP for taming, up to a 50% imprinting bonus, and redistributing wasted stats.

This way people can choose what they want to do for each time, perhaps using standard methods for tough tames that are easier to snipe KO, or for utility tames where imprinting and stats don't matter and immersive taming for others for the bonuses, but it's up to them.