Thank you sir. Reading, and re-reading the article.

So it looks like we have to withdraw the $6k from the Roth through a corrective distribution. Not too worried on tax or penalties on earnings on the $6k as these earnings are very small. 

And the IRS still gets 2x 1099's so I still have to show both in his return. Do I show the corrective distribution in his 2020 tax return, which explains to the IRS the $12k instead of $6k on his 1040?

Also does this cure the excess contribution that occurred in the post tax IRA? This IRA is now closed as we set it up only for the back-door.

Maybe questions to Intuit themselves, and / or the plan administrator - though the the plan is at a broker dealer, not a retirement plan company. They have not been helpful. 

Any further insights much appreciated. 

Thanks Nolan