"You state "taxability unknown"."

That could be from reading the code(s) on the 1099-R.

A 1099-R is informational. It is for money Out. The entity issuing the funds won't necessarily know what is happening with them, if they were rolled (for an indirect) or used, or used and then replaced as rollover in the allowed timeframe. They might not know if the person did a partial backdoor with the distribution.

Being unknown on the 1099-R isn't an issue. It's up to the taxpayer to tell the preparer what was done with the funds. And it's up to the preparer to do the due diligence to prove it; ask for the Form 5498 (for money In) that reflects the same amounts.

Example: The taxpayer took the funds personally, then presented that to the Roth brokerage. There would be required withholding in an indirect rollover, so the amount the taxpayer converted via backdoor needs to be gross amount distributed, or there likely is tax on the portion withheld, even though the taxpayer gets it refunded later.

It can be a direct transfer, but they might not know the type of account it was sent to.