For a lot of stockings with knitted "clocks", the heel shaping is the pattern, and the way you do different increases/decreases is part of what makes it fancy clocks rather than a shaped heel. But I think they're using fancier decreases than ssk for those, too. And some of the Scandinavian colorwork socks work hidden decreases into the color pattern (like in a sweater yoke, but more confusing) although I think those mostly just use k2tog.