I think I've resolved this.
* The TurboTax interface and series of questions for this is confusing.
* I made an estimate for prior year contributions. As long as this is anywhere close to the actual amount, then the taxes seem to be calculated properly. However, leaving it blank, $0, or too low seem to have caused taxes to be charged.
* I didn't owe any taxes on the amount, since it had already been taxed, and since the distribution was a valid early distribution based on excess contributions distributed after the deadline but within the same year.
