Here in S.C., even when planted in October, the garlic sprouts and begins to grow until cold temperatures and frost slow them down. Frost only causes superficial damage to garlic. I believe that the early start will just give the plant more growing time between now and late spring/early summer when the mature bulbs are harvested. Here is what thegarlicstore.com says about planting time and overwintering garlic plants.
"When to plant? The fall is best. Remember garlic is a bulb (like tulips and daffodils). Plant 4 to 6 weeks before significant ground freezing may occur. On the High Plains, we like to get going by mid-September, since snow by the end of September is not at all that rare here. Further east and south, late September and into October will generally do. The idea is to get the cloves in the ground during warm weather so germination occurs and good root formation follows. It is good sign when you get green shoots popping above the soil in late autumn. Don't worry. The tips may suffer a little winter burn, but they can tolerate zero and below. Studies have actually shown that some garlic leaves actually grow ever so slightly on sunny days with temperature is below freezing."
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.