For the love of all that is holy. That worked!!
To be honest: That makes zero sense to me.
I've used cross LDAP lookups which dont care about this.
For future astronauts reading this.. here is what I did exactly:
1. I have ONE DC in my test lab, it's a GC. So it's listening on port 3268 (MS's GC port.)
2. Search attribute was set to userPrincipalName
3. Base DN is OU=Sales,DC=fabrikam,DC=com
4. Bind DN is a user inside sales, so.. OU=Sales,DC=fabrikam,DC=com
5. That user has First, Last, and email fields put in.
And.. 3 hours later.. and a very helpful answer from sravuri .. it worked !
Thanks again sravuri !
EDIT:
I went back and changed UserPrincipalName (old way) to SamAccountName.. and this is better, since this is already populated in all my accounts.