At least on Google's own phones, Android is improving continuously. When they get to the point where they're comparably secure, the guide will be updated. As you can see: it's not anti-Google bias producing that recommendation: the guide also says to use Chrome, and Chromebooks if possible.
If you don't mind elaborating, what do you consider the most important security properties still missing from Android on the Pixel phone?
My personal wishlist would include an equivalent of iOS's ability to encrypt new files to a public key while the phone is locked, as pointed out by Matt Green in "The limitations of Android N Encryption", but I'm interested in your perspective.
