The 40-odd-hour result was only achieved by loading a webpage, lowering the brightness to 150 nits, and doing absolutely nothing else with the device. That’s not reflective of real-world laptop usage, though it is a common trick for devices with always-on displays like phones and smartwatches.
By comparison, if we assume that NotebookCheck’s test protocol attempts to emulate real-world use:
> We measured 16 hours and 45 minutes in our review.
I can’t find any statement of how the 14-inch M5 MBP performed in their own like-for-like tests, despite checking several of the articles linked from their review meta-page: https://www.notebookcheck.net/Apple-MacBook-Pro-14-2025-M5.1...