The timestamped part of the video shows an iPhone 15 and 17, both on iOS 26.3. 45% on the iPhone 17 and 25% on the iPhone 15.

Only the iPhone XR in that test is on iOS 18. It scored behind all of the models on iOS 26.3 except for the iPhone SE. But that's not a useful comparison because who knows what condition the XR's battery is in at this point, and nothing else ran on a comparable iOS version.

Not sure what point you were trying to make with that video, but it doesn't really demonstrate cross-version battery performance.