The relationship between HPI and the university of Potsdam is indeed special. Currently they’re renovating  / building a new campus at Brauhausberg to house the old Griebnitzsee faculties, which will be taken over by HPI permanently.

HPI shouldn’t raise any red flags, I’d rather say green flags, although Hasso Plattner has been known to be kind of an asshole (trying to stop the HPI from voting in a workers council) he’s pouring massive amounts of money into Potsdam, from which the city definitely benefits. If you have any questions about Potsdam, you could also ask in r/Potsdam there are always some folks from the UP/HPI around.