Just thought to chime in a bit on this - I think the awesome Marc (been always your fan and thanks for Skala Preview!) has addressed how to properly designed on Pixel XL (or Nexus 6P, they have the same pixel density), I would suggest to continue design Android apps at 360x640 (the standard Material Design 16:9 size) to avoid the illusion of the additional horizontal space (vertical space is less of a problem usually because we can do vertical scrolling), because at 412dp, you actually have that additional 52dp and you might actually try to fit as much things as possible, but the fact is that your app will be running on many devices with the standard 360dp width (there is even devices at 320dp width, although they are rare nowadays), so there is a chance that your design doesn't fit on such devices.

Similar to iOS design, I always start at 360x640 for Android, and 320x568 for iOS for the base screen space that I can have, then I will make another artboard if I want to see how it will look like on a bigger phone, like Nexus 6P or iPhone 7 Plus. Otherwise there is a fair chance that your design on Pixel XL or iPhone 7 plus won't fit into smaller devices like Nexus 5 or iPhone SE.