I believe the name in question does not have nomenclatural issues.
Philodendron imbe | International Plant Names Index
It seems to me that very often the ‘unplaced’ flag in POWO means simply that the Kew curators have not got around to reviewing the status of that name and/or there is no recent revision with a reliable opinion. I expect there are tens of thousands of such names. In these cases I don’t believe that a POWO ‘unplaced’ flag is sufficient justification for the name to be automatically excluded from iNat. In those cases involving long forgotten names then they probably shouldn’t have been added in the first place. Some people don’t seem to realize that iNat is not a repository for all names that have appeared somewhere. IMO those names should be inactivated. However, there are other cases where the name is in current use, despite the absence of revision by POWO, and they should be kept. The iNat flagging of all names that are ‘unplaced’ in POWO might serve some purpose to identify names that need inactivating. Otherwise I don’t think ‘unplaced’ generally means much.