I'm guessing he is talking about DPI scaling in Windows and not about printing. Like, if you use a 46" TV as your monitor you may want to use 150% DPI scaling so everything is a bit larger then normal 1920x1080.
This may actually become a lot more important if very high DPI screens continue their current trend.
MS Surface Pro is going to have a 1920x1080 (they just say full HD but what else could they mean) 10.1" screen! Stuff is going to be really small without DPI scaling on that too.