The help file says:

Check if original federal return filed electronically:

This box will be automatically be checked if this file was successfully submitted for electronic filing.  This box can also be manually checked if the taxpayers original return was successfully submitted for electronic filing but the status was not update in the data file.  This may happen if, for example, the taxpayer prepared and submitted their own original return, or if the original return was prepared and submitted by another firm.

By manually checking this box, you are affirming this taxpayer's original return was successfully e-filed.  This will allow the amended return to be e-filed.  It the IRS does not have record of successful original e-filing by this taxpayer the amended return may be rejected.

This sounds to me like you can now e-file amended returns where you did not file the original.