Thanks for the explanation and proof that they are absolute shaite and an ultimate waste of money. So happy that I never (!) got into that stuff.
I glady leave those piles of crap for others. Which makes it all great! We all benefit in the end and everybody is happy. I do not spend my money on that crap - and hence, there are more Paul derailleurs on the market for other peeps to waste their money on!
They look sturdy enough so if the cage has good spring tension and the pivots aren't floppy then what is wrong? Friction shifting allows for less than ideal construction, too.