Conspiracy?
Try Occam's razor.
How they explain the failure rate to those higher up is a mystery to me, but stopping DECs is the most efficient way to stall reqruitment.
It has certainly stopped me from applying. I know my worth, and there is no way I am subjecting myself to a humiliating failure set up by the assessment team.
Good luck! You are the ones paying for this with 100 hrs/month.
Maybe, just maybe, it will work.
I have my doubt.