KotLC hc/theory
I believe that vanishers and phasers are different forms of the same ability
Well, to be specific, I believe that vanishes are a weaker form of phasers.
Vanishers, as we know, disappear by allowing light to pass through them. Della vacker (neverseen, in the first 2-3 chapters) is a very powerful one, and allowed the water to pass through herself. Now who can do that? phasers!
Next, blur from the collective. He smudges himself to allow light to partially pass through, I believe, and being a phaser he can do exactly what Della did with the water
Vanishing is basically an ability that allows anything to go through your cells with enough practice - and may as well become a phaser or smth
Tl;dr - vanishers are a weaker form of phasers