Unsure if bug or stupidity

I've been leveling a witch with bone spells and throw whole time leveling I allocated Bone chains on amulet since it was recommended online. After reading it, thought yeah, this would be great... And it seemed to work fine with bone blast (been a few days and don't have access to pc to try again right now). Now that I am using reap, I see 0 effect of pinning even with up to 80% crit.

Am I missing something or is "Bone Chains" notable passive bugged?