Manifestationism says the manifestations continue even if there is something objective underneath. This is why it is a product of the synchronicity argument. The synchronicity argument says you cannot remove the appearance of the paranormal world by appeal to saying some putatively object ontology holds. This not possible precisely because the appearance suggests exactly that said ontology does not obtain.
Manifestationism is a wider meta-philosophical strategy that extends this point. It says that all of these philosophical appearances persist in various competing ways. This a pro and against dialectics. Warring manifestations will generate new manifestations. This however does not entail that the previous incarnations have gone, rather these pneuminous creatures proliferate, accreting to each other in dubious alliances to take control of the endless turmoil that is the pneuminous territory.