It was correct for the 401(k) plan to report this on a single Form 1099-R. Due to limitations on how you must report this in TurboTax, you must split the Form 1099-R yourself.
The tax code considers the entire amount in box 1 of the From 1099-R to be income, some taxable, some nontaxable. TurboTax's summary shows the total of taxable and nontaxable income. Only the taxable income adds to your AGI which is used to determine your Medicare IRMAA.
"The extra $1,000 pretax direct rollover is through me over the $106,000 Medicare limit."
No, it doesn't. Entered properly by splitting the Form 1099-R, one for the portion that went to the Roth IRA and the other for the portion that went to the traditional IRA, the amount that went to the traditional IRA will not be included on Form 1040 line 4b.
