"the non-deductible basis will offset the taxability created by the conversion 1099R on the return."

Maybe. If the Trad IRA account already has deducted contributions and earnings, then there still is a pro rata tax in the conversion. Even that $6k basis can have taxable earnings, if it was in the Trad account awhile, which creates a taxable conversion. Of course, recently there has been a lot of loss events, so it's hard to know. Just remember there is no "specificity" with the conversion. Unless they only ever had this $6k in there, it is not literally the same $6k that is converted. It's a value conversion.