Mask columns referred inside functions

Today if the mask filter is configured for a column , and the column is referred inside a function in the select projection list than, column is not masked. This should be correct

Following query
select SUBSTRING(nation_id, 1) from table_1

returns nation_id even if masking filter is set to filter nation_id

This should be fixed, that if the masked column is used inside a function in projection list, then the entire field should be masked with "X" - no partial regex masking or obfuscation should be done.