I think he is referring to active riders. It was widely reported that some Aderlass riders/athletes are still active. There was lots of talk about a specific german rider being involved, but not in the media or anything.Think it depends what Preidler really means where he says "there could be other interesting interlocutors in the bloodletting context in Germany."
Thankfully we have Froome getting off for a positive other riders get banned for all the time, which shows you all you need to know.I mean sure, those guys are now proven dopers. But then again, no one was particular successful (unless Petacchi ofc) or showed extreme jumps or improvements. Just kind of proves that you only really get into troubles if you don't have a top-notch program set up for you but have to do it on your own. And even then you will pass all the tests and it takes authorities to get involved for something to happen.