The reason the naming convention is interchangeable is because they represent measurements in digital space, and in medium (print). At 1:1 1ppi is 1dpi. But printers have much more dense DPI resolution these days, so it's not 1:1 in pretty much all cases today except scanning, where setting it to 300 DPI will be 1:1 with PPI.
PPI X/Y reoslutions won't effect the actual image being viewed on a computer, just like a DPI label wouldn't, it's EXIF data to be read by readers, such as a printer.
