It's always been my view that you really need 6m of water to assess whether a trainee is in proper control of a CBL. Other than an uncontrolled blast for the surface or a bobbing up and down, in a pool it is difficult to assess how well a trainee is controlling ascent rate.
It wasn't my intention to 'tar and feather' the instructor but he does take an ultra-strict approach to training which I feel is demotivating to trainees. However when he is finished with them, they can certainly perform the skills. A couple have asked for other instructors because they got fed up with his approach taking so long compared with other trainees. He also refuses to accept ADI's playing any role in training except as his 'bag-carrier' and will not sign off any skill that he does not personally teach.