Filer Beware - TurboTax Online Standard vs. Itemized Deduction Bug

I've been using TurboTax for several years and never had a problem with it. This year (2023), I filed my return as usual, but then remembered I'd forgotten to include a 1099-R for a 401k rollover. No problem I thought. I'll just start an amendment and add the 1099-R. Furthermore, adding the form won't affect my tax refund or liability.

So, I press the button to start an amended return, and here's where things get weird. Instead of zeroing out the liability and refund, TurboTax immediately says that I'm due an additional $1k federal refund. This is strange, because the TurboTax documentation clearly says:

The refund calculator will start new at $0 and only reflect the changes in the refund or tax due

I then click on "Tax Tools" / "Tools" / "View Tax Summary", and notice that TurboTax is now using an itemized deduction, which is $3k more than the standard deduction it selected when I originally filed.

Let me be clear -- I did nothing other than click the button to start an amended return. The only explanation is that TurboTax did not use the correct deduction when I filed my taxes. Furthermore, if I hadn't started an amendment, I would have lost out on ~$2k in additional refund money (federal + state).

I'm posting here for a couple of reasons:

• To everyone filing their returns with TurboTax online: check if you should be receiving additional refund money simply by starting an amended return. If you're due additional money, it will be shown immediately at the top of the screen.
• Also, I'd like to share that TurboTax has been dismissive of my claim, and the customer service experience has been abysmal. After ~5 phone calls, ~3 hours of my time, and numerous escalations, I still don't have any resolution. Furthermore, one of the customer reps promised me a full product refund, but I later received an email saying that the refund request had been denied.

I am quite disappointed with my experience using TurboTax this year. I will most definitely be switching to a different software vendor next year.