Here I thought about the "Systems that ... bring to your attention the things it's learned you want to see." A system that has "learned" might bring to attention some things and omit others. What if those omitted things are the "true" ones or the ones that are really necessary? If so then we cannot consider the AI having an explicit goal to tell the truth as Eliezer noted. Or it is not capable of telling the truth. Truth in such case being what the human considers to be true.

I agree and it depends on the lecturer, of course. Experienced lecturers seem to be more auditory oriented than aspiring ones.

There's also the pace of the learning to be considered: one sets his/her own pace when learning by text as opposed to speed and tempo chosen and changed by lecturer.

I think that a combination of both is the most effective way.