Does this problem still occur when you use even higher-resolution screens, like the "Retina" display?
It's worth noting that it doesn't really matter though. Most iPhones are pre-retina, and this will be the case for at least several years. So I can't think of a medium where it's okay to assume this level of screen resolution. The author's point still holds.
I believe laser printers do print at something like 1200 DPI, like you're saying.