As I first saw noted on an Ars comment, it is unbelievable because their testing regimen has no reflection with real world testing, and I'm sure significantly different than Apple's, which I believe doesn't include 'standby' testing included in usage:
"Testing consisted of full battery discharge with a mixture of active use and modern standby. The active use portion consists of (1) a web browsing test accessing 8 popular websites over multiple open tabs, (2) a productivity test utilizing Microsoft Word, PowerPoint, Excel and Outlook, and (3) a portion of time with the device in use with idle applications. All settings were default except screen brightness was set to 150nits with Auto-Brightness disabled. Wi-Fi was connected to a network. Battery life varies significantly with settings, usage and other factors."
M1 Macbook Air has larger, 49.9WH battery, and only boasts 18 hours as maximum battery life.