Merry Xmas with ... cable clamps

Cable clamps are a very common cable termination used in ropes courses, adventure parks etc.
Here is a typical application, an eye, clamped, with a thimble.

But there is a very special application which is not mentioned in the Eurostandard for CLAMPS (EN 13411-5) but only in the standard for Ropes Courses (EN 15567):

In case you have to "tie" two ends together, make a cable longer etc., you should do like this:

Here is a video about the tests.

Interesting is to apply different torque. It says 9 Nm in the standard, but I could not find out why we should not apply a higher torque to the clamps. I only hear assumptions, but no facts.

Here is the slipping force of 1 clamp, different torque.

 It is obvious that the higher the torque the higher the force they can hold before slipping.

I asked the DIN, the German standardization institute, but they never answer.

So I make a bold statement here:
9 Nm are a modern urban legend. It is better to apply about 18 Nm, maybe even 20 Nm.
I could not find a reason why not.
The discussion os now open.