The witches broom appears to be common among Creole cultivars (although my other beach farm Creole didn't broom), but could also be the result of very rich soil, over-fertilization, a warm winter, or poor storage prior to seeding. In the herb bed, at least two of those conditions were met. You may have noticed that these bulbs were harvested bare naked, with absolutely no wrappers. This is due to irrigation. Timed for every two or three days during this hot and dry spell, the wrappers simply rotted away in wet soil as the leaves dried down above.
Of course, the other beach farm garlic was fine because the irrigation to those beds was cut off. Garlic is best served by one or two weeks of dry weather before harvest. The weather doesn't always provide us with the best circumstances, and a little water from a thunderstorm won't ruin a healthy crop, but constant irrigation will.