Google says Nexus 5X and 6P will not have twist gesture to launch the camera

First, users started to notice that Qualcomm had updated a blog post about the devices to redact the portion mentioning the option to twist the phone to launch the camera, and instead added that the quick launch option of double-tapping the power button had been implemented as a replacement to the twist method. Google confirmed that while both options had been tested, the power button method had won out in the end. 

Presumably, Google didn't want to have two different quick launch methods, which could be confusing. There was no explanation as to why there was confusion in talking about the features, though perhaps it was a very late change, and the software that was shown in India will be old compared to what will be released elsewhere. 

source: Qualcomm via Android Police