Unarmed builds not allowed to use Spirit Heralds Bug?

Hello,

I am playing an unarmed build with a shield. I am allowed to use some spirit but not use heralds? Why would I be able to use shattering palm which is ice damage to explode things but not be able to proc herald of ice?

I just want to explore more builds but it seems to punish any trying new things.

Why have unarmed nodes and the option to play unarmed and then not let us use heralds? Yet we can use other spell ones and stuff?