Language, as a problem, doesn’t have a discrete solution like the question of whether a list is sorted or not.
Seems weird to compare one to the other, unless I’m misunderstanding something.
What’s more, the entire notion of a sorted list was provided to the LLM by how you organized your training data.
I don’t know the details of your experiment, but did you note whether the lists were sorted ascended or descended?
Did you compare which kind of sorting was most common in the output and in the training set?
Your bias might have snuck in without you knowing.