>That's more than what a large refrigerator uses ..
That's partially due to good insulation in modern fridges. After all, if the insulation is perfect, you could run a fridge on 0W (assuming you don't open the doors).
Watts are joules/second - with perfect insulation and doors not opening, the only energy used is the energy used to cool the contents initially. As time approaches infinity watts approach zero, despite the energy consumed initially. c/t -> 0 as t->INF given constant c.
Anandtech's testing showed full load power consumption of 279.82 W (3960X) and 286.72 W (3970X). OTOH the "255W" Xeon W-3175X full load power consumption was 381.08W...
Overclocking chips does tend to cause power usage to spike, yes. That's not exactly a new thing, nor is the increase that surprising. A slight bump to voltage will cause power consumption to skyrocket. Heck, i9-7980XE's at 4.9ghz are pushing 1kW in consumption. Hence why intel's 28 core @ 5ghz demo used a 1700W capable cooler.
The power consumption of an individual core can vary greatly depending on its clock speed (and voltage, which can be reduced when running at a lower clock speed). Putting 64 cores into the same TDP as their 32-core chip is actually pretty easy. If you actively use all 64 cores, they'll be running at a lower clock speed than if you were only using 32 cores.
That's partially due to good insulation in modern fridges. After all, if the insulation is perfect, you could run a fridge on 0W (assuming you don't open the doors).