my import was successful. The forum was fully transitioned with zero errors once I correctly exported and imported the database in the right format - went like clockwork.
^^this. My original question was whether or not the PMs in VB format (which are individual, in an inbox and a sent folder, and only somewhat interconnected in a really unmanageable way) were supposed to be converted over in such a fashion that they would become "pulled together" like a zipper and merged into a single conversation between the 2 people involved. According to Jeremy, the import engine does not do this, so case closed, unless you can give me an example of someone who imported a vB4.x forum and their PMs were indeed merged and turned into conversations in XF format.
XF doesn't have "sent" and "inbox" folders for conversations. They are instead like threads only viewable by those in the conversation. So I can understand how they would not be imported and 'converted'.