It is not quasi, it is just branding.
It is not BS, just a clever name with specific meaning—which is more specific than "high DPI". Where exactly does high starts and middle ends?
DPI does not take into account viewing distance, because it is all about linear measurement. "Retina" is about angular. If is is smaller than average eyes ability to resolve then it is retina, what's BS about that?
"Retina" is just as ambiguous as "High".
Apple didn't invent anything with "Retina" screens so branding is pretentious, pixel density is just that: a number.
It's weird because the iPhone 4 pioneered the "Retina" marketing and didn't need "Retina ready" websites.
But I'm not sure about "High DPI" either. I feel bad for future customers who have to decide between (crappy) HD and (good) High DPI displays. There simply is no good term for "devices where one CSS pixel maps to four physical pixels".
Then again, at least we don't need to worry about "High DPI" becoming obsolete in the same way as 16-bit "High Color" has. Or is there any conceivable scenario where we'd need higher-than-Retina DPI? Cyborg eyes?
>It's weird because the iPhone 4 pioneered the "Retina" marketing and didn't need "Retina ready" websites.
That's because webpage images in an iPhone 4 screen are resized to be smaller anyway (to fit), whereas in a 15" MacBook Pro you see them in their original dimensions but with half the detail of nearby fonts, hi-dpi images or vector assets.
Actually, "Retina", for all the branding-ness, is more scientific (as it incorporates facts about actual human vision, display density, angle of view, distances, etc), than "High DPI" which is just an un-quantified description.