You can totally make some nearly full melt dry ice hash. I just don't know if in the end you can yield as much PURE FULL MELT hash with dry ice, dry sieve, or bubble...it all comes down to technique and screen size. (Dry ice vs bubble) dry ice just give you results you can have from start to finish and smoke it in 5 minutes or less if you're organized....hell you could start smoking it as soon as you got a few shakes in haha if you're that desperate. All i know is that there aren't any stickied threads on dry ice hash only the Ice Wax with Matt Rize.
Dry ice is better that regular dry sieve though...IMO! If you don't know, the super duper cold dry ice makes the trichomes very brittle and they break off easier than when at room temp. That's the selling point...
My eyes about popped out of my head when i saw how fast the trichomes were sieving with dry ice, after the plant material chilled and became brittle it was only a few light shakes and the black plactic turned yellow.
But you are right...purity has nothing really to do with your method in this case, it's how finely honed your skills are with gently shaking and choosing the perfect screen size you make the purest product.
Happy sieving!