Engaging in a Learning Activity is a special type of concernful action. Rather in the way we might play a game, we submit to rules and constraints. In fact the game metaphor is useful with regard to learning activities. They demand the somewhat restricted exercise of particular skilled performances (linguistic, maybe technical) in a language game. At its most basic, a teacher asks a question and the learner wonders "There's something I am required to do/say.. I must think what it is!". The teacher determines the rules of the game. The learner might not choose to play the teacher's game (and maybe try to establish their own game) - such behaviour might be construed as indiscipline.
Even with Pask's teach-back, I think it is still the teacher who determines the rules of the game. Teach-back is simply a more elaborate skilled performance that is required by the learner. Teachers and learners are obviously asymmetric.
What is the purpose of restricting the skilled performances in a learning activity? I think it can facilitate 'personal revealing'. With a restricted set of communicative acts within the activity context, the speech acts can expose more of the person of the teacher and that of the learner than might be revealed in everyday life. This might be because in everyday discourse, skilled performances relate to personal viability: threats to viability might be perceived with certain communications, and as a consequence they won't be made. Within the constrained context of a learning activity, there is less perception of threat because all parties understand the relatively simple rules of the game.
Where does the learning happen?
There are two things that go on in a learning activity:
1. There is the use of subject 'content' as a way of framing the rules of a language game;
2. and then there is the recognition of the person of the teacher.
The teacher's knowledge is part of their personhood. In this way, there is effectively a 'double description' as Bateson might explain it. We come to know best when both the aspect of the language games of the subject and the person of the subject are there. If we only get the language game - maybe from reading about it - our knowing tends to require playing that game with others (talking about the knowledge).
What does this tell us about the role of content - and particularly open content? I suspect learners need both descriptions. I think without the person of the teacher, learning with just content online is likely to be deficient unless the learner uses the content to play language games with others around them. Alternatively, it is possible that the author is also available for inspection online (biography, etc) - in which case both descriptions (the person and the knowledge) could be gleaned from online engagement. Teachers might use open content as a way of defining language games which they may want to play with their learners. But this can only work if the teacher uses the content in a way which helps to coordinate the language games they play with their learners.