@isakroa I suppose the thing is do you need preprints to do open review, though? Conceivably (or PCI, etc.) could restrict access until the first reviews/recommendations are in. The end result would still be open, but it would reduce the risk of results being disseminated to the public before they're ready.
That said, the elephant in the room is the assumption that peer review—open or closed—is actually effective at filtering out bad science, which I'm not at all convinced of.