The difference here is that "blast processing" was a vague, nebulous term that was never really elaborated on, and this is a very specific technical specification (the iPhone 4's 326 ppi screen), and is being compared against a reasonably specific reference metric (the sensitivity of the human eye). The practical upshot of this is that once you have a display whose pixels are so small that at a normal viewing distance nearly all of the population will be unable to distinguish neighboring pixels from each other, there is very little use in further improving resolution without also increasing screen size.
Do the specs speak for themselves? No, they don't, because while 326ppi makes perfect sense to me, I don't know anything about the maximum sensitivity of the human eye, and I'm interested to hear where that bar is set, whether this display really exceeds that, and what caveats I should be aware of in taking this metric into consideration when selecting screens for my own use.
Whether or not the iPhone 4 in particular meets this goal only of mild interest; it's a case study of a device that literally claims to be designed to have a higher resolution than the eye can distinguish. If it doesn't hit the mark, there's going to be a display that will come closer soon, and I'd like to be able to talk more knowledgeably about what this means.