The site quotes "40 watts lower power draw" as a reason to prefer the AMD CPU, but what they're actually comparing is TDP, Thermal Design Power. The TDP for Ryzen 3900X is noted as 125W, but it's actually 105W. According to Anandtech, the power threshold that is allowed to be delivered to the socket for 105W TDP CPUs is 142W.
The 3900X probably does use less power than the i9 9980XE, but TDP is not power usage.
https://www.anandtech.com/show/14605/the-and-ryzen-3700x-390...