Apple used lower screen brightness for showcasing M1's superior battery life

"MacBook Pro with Apple M1 chip: Testing conducted by Apple in October 2020 using pre-production 13-inch MacBook Pro systems with Apple M1 chip, 8GB of RAM and 512GB SSD. The wireless web test measures battery life by wirelessly browsing 25 popular websites with display brightness set to 8 clicks from the bottom. The Apple TV app movie playback test measures battery life by playing back 1080p HD content with display brightness set to 8 clicks from the bottom.

MacBook Pro with Intel Core processor: Testing conducted by Apple in April 2020 using pre-production 1.4GHz quad-core Intel Core i5–based 13-inch MacBook Pro systems with 8GB of RAM and 256GB SSD; and pre-production 2.0GHz quad-core Intel Core i5–based 13-inch MacBook Pro systems with 16GB of RAM and 1TB SSD. The wireless web test measures battery life by wirelessly browsing 25 popular websites with display brightness set to 12 clicks from the bottom or 75%. The Apple TV app movie playback test measures battery life by playing back 1080p HD content with display brightness set to 12 clicks from the bottom or 75%."

The screen brightness curves can of course be differently calibrated. But if Apple really wanted to show a fair comparison, they'd have just specified screen brightness in nits directly, instead of using this roundabout comparison.

Laptop screens can easily consume 3-7 Watts of power, which dwarfs the SOC power, and makes up for ~70-90% of the total system power draw for watching videos. So if the brightness settings were really different (in nits terms), this comparison is quite disingenuous on Apple's part.