I cannot understand the rational for choosing   δι᾿ ὅν in 2 Pet 3:6/2-4 and since there is no textual commentary I post the question here. When I look at the genealogical tools I note that reading a is incoherent (seems to have arisen several times) whereas reading b is coherent. Moreover, reading b seems to be the lectio difficilior and has very strong support (in contrast to reading b. Is this simply an editorial mistake?

I suggest to take the heavens and earth (οὐρανοὶ . . . καὶ γῆ) as the correlate to δι ων (reading b), with reference to Gen 7:11 where we read that the fountains of the great deep and the windows of the heavens were opened (or LXX, floodgates/waterfalls), so the water came both through the earth (from the abyss) and through the heavens.