Not at all. Defects are typically just points of discontinuity or where a pattern breaks. These happen when something relatively continuous is forming but the

Not at all. Defects are typically just points of discontinuity or where a pattern breaks. These happen when something relatively continuous is forming but then the pattern breaks locally due to either global initial conditions or something unusual happening locally. I think the term is probably borrowed from the theory of crystal lattices where defects are classified: dislocations, substitutions, and holes. As a crystal is forming, sometimes two contiguous regions can't come together in the same pattern because of initial conditions where the lattice won't line up right. These then form adjacent "grains". Alternatively, sometimes internal stresses result in a dislocation where a large section of crystal shifts along a line of symmetry. Or sometimes a stray impurity is hanging out and a crystal forms around it. Or holes happen where it's just like musical chairs as the crystal is forming and there's one too few atoms to go around. In none of those cases is there some "purpose", and yet there is a clear local discontinuity in an otherwise large scale pattern. The terminology fits pretty well to the situation here I think, only they're speaking about topological phenomena.