In Collect, the field at the top of the list is used only for filtering the list below it, it is not used to show the currently selected value. I believe that if you add the minimal appearance (so minimal autocomplete in the appearance column), you will get what you're looking for.
Can you describe your needs, please? The more context you can provide about what a data collector is doing when they see this field, what they need to be able to see to make the right decision, why you're setting a default, what's not working for you about minimal autocomplete, the more likely we'll be to provide helpful advice.