Powered by Android

HTC ONE(M8) and Samsung Galaxy S5 will boot up showing the message "Powered by Android" in it's classic font that was first seen in HTC G1 in 2009.
Maybe this is a step taken by the most growing user -mobile operating system as many manufacturers like Samsung,HTC,Nokia are proving the features of Android but with a highly modified interface such as the Touchwiz on Samsung Devices or Sense on HTC devices. It is unclear and not announced by Google if it's mandatory to add "powered by android" in future devices for all manufacturers.