User with delegate access cannot see Project Number field in Expenses

We have a user who needs to claim expenses from a project. They have designated a delegate to raise expenses on their behalf. When the original user logs in, the project number field appears. When the delegate logs in and raises expenses as themselves, the field is there, but when trying to raise an expense for the user they are assigned to, the field doesn't show. I have added myself as a delegate in a test environment to test and it does in fact show for me.

Why does the field not populate for one specific user acting as a delegate?