What he is talking about is where the insulation is. In hot humid climates they now recommend that the roof itself being the insulating boundary not the ceiling. The attic becomes a tempered zone. This reduces heat gain into the house and especially makes the house cool better at night as all that heat in the attic isn't radiating down into the house all night.
Up north attic venting is even more important than in the south because when the roof gets warm it can melt ice and snow and cause ice dams that can ruin a roof and house and cause all kinds of moisture damage and mold growth. The roof needs to stay cold regardless of weather it's vented or not. So on an insulated roof deck it needs to not let heat out to the outside to cause ice dams.
Here where it's hot most of the year it's an energy usage issue not really a damage to structure issue.
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