I pretty much just had the same conversation with an IRS rep.
This rep knew nothing about having my account "marked".
To the IRS you are either eligible or ineligible, and that is based on your previous years' filing. If the box was checked in 2018 or 2019 the IRS has no way of knowing if it was in error or not. The tax return must be amended to change it.
So, after I told the rep that I didn't appreciate feeling like I was being scolded, she put me on hold and said that my amended return was "pending", and that's all that needed to be done.
She did say that all reps at the IRS knew about the TurboTax glitch. And, they have all been trained on how to advise taxpayers about what to do going forward to claim the stimulus payment/credit on their 2020 filing.
