I don't mind people using the term DPI. The part that confused me is that the OP is drawing a distinction between them.
In my mind DPI == "dots per inch", PPI == "pixels per inch", and they measure the same thing (although some people frown upon using DPI in a digital context). The author redefines them to mean "device pixels per inch" and "physical pixels per inch", where PPI / devicePixelRatio == DPI. I wasn't sure if that's an OP-thing or an iOS thing.
In my mind DPI == "dots per inch", PPI == "pixels per inch", and they measure the same thing (although some people frown upon using DPI in a digital context). The author redefines them to mean "device pixels per inch" and "physical pixels per inch", where PPI / devicePixelRatio == DPI. I wasn't sure if that's an OP-thing or an iOS thing.