"We couldn't simultaneously argue two conflicting theories of defense"...
Isn't quite the same argument when your revealed preference shows you not to believe either theory to stand on its own (or together).
"Your honor, we'd like this conviction thrown out because we couldve/shouldve claimed 'defense option B'." Retrial granted. "No! We don't actually want to retry with 'defense option B'! We just needed a reason to throw out conviction based on 'defense option A'!"
An appeals judge should be able to make that call the same way a trial judge can dismiss charges before trial. That appeals judge can easily say, it’s relevant but not clear enough for me to dismiss the case.
PS: Thus various standards of evidence “beyond reasonable doubt” vs “clear and convincing” vs “preponderance” etc.