That sentence is specifically about composers of methods in change ringing, where the musical possibilities are tightly constrained by the rules and the physics of ringing large bells. Change ringing is based on permutations constructed by swapping adjacent pairs. (Except for the jump changes that the article is about.) For a “triples” peal on 7 bells the ringers are supposed to ring all 5040 possible permutations. It’s called “triples” because you can make up to 3 swaps at a time; one of the challenges (for example) is to construct a triples peal that only uses triple changes.