While DAZ Studio has always supported Poser formatted content, it is important to understand that despite our best efforts to make it seem as though Poser format files are nearly native to DAZ Studio, the fact that they are not remains true. The information contained within Poser format files is not in a form and/or language that DAZ Studio inherently understands. These files are in a form/language that is native to Poser, and they have to be imported by DAZ Studio - which is to say they have to be interpreted/converted into a form that DAZ Studio can understand.
Poser format files are unique when compared to the other importable formats because there are several assumptions that have to be made in order to process the data in the files, that is specific to Poser's way of doing certain things. Poser content is also unique in the way that it is presented within the Poser UI, so handling it separately from Other Import Formats allows the experience to be somewhat familiar to users of the Poser application.