"was for an excess contribution in 2019 and reported on the 2021 1099-R"

The contribution in 2019 was for tax year 2019 or 2018 (made by the due date of that return)?

"The broker advises that the 6,000 is a return of contribution all basis so non taxable."

Unfortunately, that is not true this late in the game. Read this:

https://www.investopedia.com/what-to-do-if-you-contribute-too-much-to-your-roth-ira-4770686

If it was removed in the timeframe to make it moot, that would be true. Not true now.