[Aesopian]

You've hit on what I found interesting about Indrek's system. He does more than just break down resistance in a physical sense (like "fight hard, now fighter harder"), but also by how goal-oriented and purpose-driven the partner is, and the scope of the drilling or sparring.

You start with no goals or purposes beyond letting your partner do repetitions of a technique (Stages 1 and 2).

You then start adding physical resistance, but are still mostly without a goal (Stage 3). You run interference, move around, mess with grips, etc. but not try to impose your own techniques (e.g. doing a guard pass while they work on a sweep). This can scale up to 100% in terms of physical resistance, but as a partner you never really have your own goal and are not trying to prevent their technique at all costs.

You build on the last stage by taking up your own specific goals and purposes, but the scope of the drilling/sparring is still isolated to the material being taught (Stage 4). Now is when you would actively try to pass guard while they work for a sweep.

Once the isolation ends, the training partners enter free sparring and rolling where both sides have their own goals and purposes, which may or may not include the material they learned in the earlier stages (Stage 5).

I find this system interesting since it addresses once of my main criticisms of how BJJ often is taught, which is the jump between instruction and drilling with zero resistance to all out sparring. The fleshing out of the isolation stages bridges this gap and makes it easier for the student to take what they are learning, drill it statically and against progressively increasing resistance (in terms of phsyical and technical difficulty) and finally bring it into their game through sparring. I think a coach can do a lot to improve the students' retention and ability with the techniques by running isolated drilling/sparring like this.