I didn't post that advice, but I understand it. Many smaller Greek islands now days live off tourism. Much of the Greek population are only there in the summer months to manage their hotels, shops, and tavernas, and spend the rest of the year working in Athens or other big cities. During the winter, such islands may have only a couple of ferry boats a week stopping, most or all restaurants and hotels, and even many shops, will be closed, and the population can drop to a small fraction of what it is in winter. Add that the weather can be mostly cold and damp, and you can see that it wouldn't make a very good vacation.

I think staying on a small Greek island in the winter could be rewarding if you had Greek friends there who were year round residents -- it might give you a rare chance to experience traditional Greek life. But otherwise, I'd say a small Greek island in winter wouldn't appeal to most travelers.