Idea Summary
In an interactive grid developer isn't able to choose NO for “Duplicate Copies Existing Value”, if “Query Only” YES is set for a column. But it should be possible, because virtual column may be derive from an other column of the record with setting  “Duplicate Copies Existing Value” to NO; in this case copied value for the virtual column is wrong in the context of the new record or new record behaves in a way, which can't be understood.

Use Case
1. Case: Virtual column is column for “Allowed Row Operations Column”

Records include two date columns for a validity period. After three month of beginning of the period the user should only be able to set end of period, all other entries are disabled and must not delete the record; to enter new values in record attributes for the future, user has to duplicate the record. The column for date of start period has the default value SYSDATE and “Duplicate Copies Existing Value” is set to NO. 
Therefore virtual column for “Allowed Row Operations Column” gets the following settings:

• interval between Date of start period and SYSDATE is less three month then “UD”,
• interval between Date of start period and SYSDATE is greater or equal three month and Date of end period is empty then “U",
• else “N”.

A dynamic action at “Resource Load” with “Client-side Condition” on column for “Allowed Row Operations Column” where item value is “U” disables all attributes except of Date of end period.

If the user duplicate a record with validity periods starts before 4 month, he see Date of start period has a value of today, but the user isn't able to change any attribute, because the “U” in column for “Allowed Row Operations Column” is copied to the new record. After the user  save the new record, changes are possible.

2. Case: Virtual column show calender week derived from a date field

Records include two date columns for a validity period and two virtual columns showing the calender week each date column belongs to. The columns for date of start and end period have the default values  and “Duplicate Copies Existing Value” are set to NO.  
If the user change date of start and/ or end period and afterwards duplicate the record, he sees wrong calender week, because this values are copied from the source record, but the date columns get the pre-set default values.

There are numbers of further use cases and in every of this situations it will be better, having the virtual column empty in the duplicated row.

Preferred Solution (Optional)
Show section “Default” for virtual columns also; disable “Type” to prevent setting of default value. Developers are able to set “Duplicate Copies Existing Value” to NO for virtual columns; then the virtual column will be shown as empty in a duplicated record - like new record.