Requesters cannot use the User service catalog field, or change requester?

Good afternoon. We encountered a situation where we used a User field for a new phone request.  One of the clerks is a requester, and she cannot change the field values for Requester OR Employee Name field.  I verified with a test user that I have created named Ken Grossman.  He is also a Requester, and when he clicks these fields, he cannot change the values to anyone else.  I don't see any documentation that this is expected behavior, and others using the same browser see the ability to change it, so it doesn't seem like browser settings:

A requester's view of the Requester field:


A requester's view of the User picker field for Employee Name:


But for me, logged in to the same browser:


And viewing this simple User picker field as me in the same browser:


Finally, I will note that my service desk is set to allow people to submit stuff on behalf of others:


Is there something in Permissions I'm missing?  Thanks.