"Ultimately it should not be taxable"

That's because the entire amount converted also is basis. That's why it works, so that's what the data entries need to reflect. If none of what I asked is true, then there will be pro-rata tax computed.

The 1099-R issuer may not provided everything that has to be entered. For instance, they don't know if there are other accounts of that type with deducted contributions or never-taxed earnings. Only the taxpayer and you will be able to enter what applies in that worksheet.