Thank you but I might not have explained my issue correctly.
In our Pivot table we have a field called 'f2528930', using the dataSourceSettings.fieldMapping option we map it to 'Customer ID'. So the user sees 'Customer ID' instead of 'f2528930' when using the pivot table. ( see screenshot )
This works perfectly everywhere except for the calculated fields. If the user drags the 'Customer ID' field to the formula it is displayed as 'f2528930' which can be confusing for users.
This has nothing to do with Excel standards. It is a display issue.