Real Time Rules - Call to Action should allow 2 level lookup like regular rules

When I create a Real Time rule using the Call to Action Topic, I am only able to go one level down on lookups in the Actions.  

Example, I want to pull in the Call to Action → Owner → Manager → Slack User ID.  But I can only go as far as Call to Action → Owner → Manager

But in regular Rules, I can pull in fields from 2 layers down:

Why does RT rules only allow you to go one layer deep?