I was among those who, when Khanmigo was first announced, were pretty excited about it's potential. I then waited for data on the results....and kept waiting.....and kept waiting. And now four years later this is apparently what we are going to get. I think that this is enough for me to decide that Khanmigo, regardless of whether or not a student actually engages with it, doesn't make much learning difference. At some point, the absence of (reported) data becomes data in itself.
I still believe, in principle, that AI tutors could be massively helpful for learning. But apparently we haven't yet figured out how to take that principle and turn it into reality.