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.