If you read the article you'll see that they're only sending their custom font to OSX. PCs get Georgia. On OSX, resolution is enough to determine pixel density at the granularity they need because of the limited number of products Apple has [1].
So they have successfully achieved their goal.
It's not a goal I would set out to achieve, but to each their own.
1. Notice that both Air models have high(ish) DPI resolutions that are unique in the history of Apple products.
Except my 15" macbook has the same resolutions as 17" macbook from 2008 and the 20" Cinema display and 20" iMac.
The current 17" macbook has the same resolution as the 23" Apple Cinema HD display and 24" iMac.
What happens to my mac mini which is running on my 23" 1920x1080 NEC Multisync? What about when I hook it up to my TV? Will it think it's the 21.5" iMac?
What about my dual monitor setup on my Macbook pro (15" 1680x1050 & 24" 1920x1080)?
What about everyone else using some variety of monitor setup with their mac?
Maybe they could try a "Optimized for viewing on Apple hardwear (and only apple hardwear) made after 20XX and at a distance XX" except for these maybe these models:" disclaimer.
Dude. Way too much pedantry. They are experimenting. If they get it right on your screen you get a more precise rendering of the font, if they don’t you get a slightly suboptimal rendering, but that’s the same result you'd get with a generic font.
So they have successfully achieved their goal.
It's not a goal I would set out to achieve, but to each their own.
1. Notice that both Air models have high(ish) DPI resolutions that are unique in the history of Apple products.