The policy says human eyes will never see the contents of your private repositories. Suppose, as you say, the repos are one day fed into an AI. How does that policy then constrain the AI later?
AIUI the AI can't be used to answer any questions based knowledge from training that included private repositories, since (still AIUI) there's no guarantee that contents from the training won't appear in the output.
But there seems to be a loophole for yes/no questions. An AI that answers only yes/no could be trained on private repositories, or run on them. So they could, say, train an AI to recognise repos that require working hours from their legal staff, or from their support staff, and then run that AI on all repos to locate repos that cause expense in the future. Things like that seem possible.
And an AI might answer questions like this: "Does any repo contain the string 845fjkef5urwejf in a Kotlin file?"