Turned out the reduction was correct and the problem was caused by me expecting a stimulus check delivered in Jan 2021 as being 2021 income. Turbo Tax did not see the January deposit, so they thought I had not received it in 2020. That triggered the missing stimulus check which triggered the worksheet creation for a rebate which caused the excess refund. The IRS was correct, the Turbo Tax app was doing what it is supposed to, and I got an education. I'll change this thread to solved if I can figure out how to do that.
