[support] Rules, Create Entity action, and data selectors

I've been searching high and low and can't find an answer to this. When configuring a Rule, if I use the action "Create a new entity", the data selectors (no matter what entity type I choose) are missing the usually available selectors "site:current-cart-order:owner:uid", "site:current-cart-order:owner:mail", "site:current-cart-order:owner:name", etc..

However, "site:current-cart-order:owner" (the actual user object) and "site:current-cart-order:owner:roles" *are* available. Does anybody know why this is? I really need access to "site:current-cart-order:owner:uid" in this action configuration.

Thanks for any thoughts or assistance. William