Why do reactive-glaze stoneware sets look different piece-to-piece?

Reactive glazes are fired so that each piece develops a slightly different pattern — AmorArc and Gibson's Soho Lounge and Gelston lines both rely on this. Verified-purchase reviewers consistently call the variation a feature, but it also means a few pieces in a 24- or 32-piece set may have visible glaze flaws or speckles, a complaint that surfaces in Target and Home Depot reviews of Stone Lain Brasa in particular.