We have created a custom user profile field called "X" and checked the box for replicate and alias and ran a full profile sync.
The field "X" appears in the drop down list for field to show when you create a custom column in a list for type 'people or group'.
We create a new column called "Get X" to the list.
We have verified that "X" has over 900 users with that data and data.
Going back to the list to create a new entry and we put the value in for "X" that matches a user, we are getting no results found.