they are not really biased against american blocks
I know Otti quite good and know he isn't biased or cheating or so.
They test with 12 mountings as far as i know and take the average of the 10 best.
Their equipment is just not the best, try our kaltmacher.de, they have a little better testbed and test with different flowrates and much more.
A Cascade can't really performs low with a small pump as an eheim 1046 and a radiator with tube and fins. I would say it like cathar, it is still a good result for the block testet in an fully other enviroment as it was designed for.
I wouldn't state that it has been user-modified or hacked, because that is not proved and I am pretty sure that it isn't so.