Older ImageMagick solutions often suggest using -units PixelsPerInch when changing the density of a PNG image, that is, for example, -units PixelsPerInch -density 300, and not just -density 300.

But in modern ImageMagick (7.1.1-33), according to the following tests, -units PixelsPerInch seems to be no longer needed for this. Is it really so or I misunderstood something?

magick identify -format %xx%y a.png                        => 72x72
magick identify -units PixelsPerInch -format %xx%y a.png   => 72x72

magick a.png -density 300 a1.png
magick a.png -units PixelsPerInch -density 300 a2.png

magick identify -format %xx%y a1.png                        => 300x300
magick identify -units PixelsPerInch -format %xx%y a1.png   => 300x300

magick identify -format %xx%y a2.png                        => 300x300
magick identify -units PixelsPerInch -format %xx%y a2.png   => 300x300