However the question is increasingly whether simply the cognitive load of feedback is the reason for this is coming up.

i.e. does the Testing effect reduce in efficacy when you apply it to every waking hour, every course? does it just benefit when you study one course?

There are clear links that subjects where students have a stake in the result (i.e. it is mandatory for college) lead to higher attendance and final grades, regardless of study method.

Lots of the predominant psychology applies only to motivated students or those in mandatory courses.. so basically, we can't know the state for free willed learning/edutainment.