There is a discrepancy between the Additional Attribute column names in View Customers and View Products modules.
In View Products, the additional attribute column names are appropriately named 'Attribute X'.
However in the View Customers module, the additional attribute columns are called 'Custom Field X'.. which is a bit confusing.
It would make a whole lot more sense (and consistency) if they were renamed to 'Attribute X'
Current View Customers column options:
Current View Products column options: