I've verified this undesirable behavior in the current version (R13) of 2020 TurboTax. Once you have indicated that a distribution from an IRA is an RMD and have indicated that the beneficiary is a non-spouse, TurboTax will not treat the distribution as rolled over even if you later say that it was not RMD. The form must be deleted and reentered to get TurboTax to behaving appropriately. (There are other convoluted workarounds, but deleting and reentering is by far the simplest way to make the correction.)
TurboTax does not exhibit this behavior when entering a Form 1099-R for a distribution from a qualified retirement plan, apparently because TurboTax does not need to ask if the if the beneficiary is a souse or a non-spouse for a distribution from a qualified retirement plan.
