@garemoko all the above aside, if we were to filter on 'activity type' (and presumably the same rules that apply to filtering on activity wrt: object vs context), I would be strongly in favor of requiring the LRS to decide whether each activity ID it considered had that activity type or not, and then consistently apply that decision.

Which is to say, a filter for activity type "...course" would return either all or none of the statements about a particular activity, even if some statements mentioned the activity type was "...course" and others did not.