Numptie of the highest order
They're totally different bushes to the ones you can replace in the control arms. I think Audi call them bearings not bushes or something like that (the ones that are pressed into the hubs) they might be worth replacing for OEM Audi ones. They were the cause of the creaking on my car which was rather annoying having replaced all the other bushes for the powerflex ones!
I also think bearing in mind there application I wouldn't be going for the powerflex ones after my own experiences and others I wouldn't trust powerflex bushes other than in a very simple place (i.e. one axis of flex).
ETA: Don't bother with using the powerflex bushes for the big front wishbone either as they're ****, mine wore out quicker than the OEM bushes.