Why it is always recommended to save the library as enl instead of enlp ?

Hi, when updating to Endnote X9.3.1 (on Mac Mojave), I checked the ‘Save as a Package’ box and created an .enlp file containing the library and the data file. I now want to undo this, and have separate .enl file (for the library) and data files (for the PDFs). What is the best way to do this?