I read "platforms" in that sentence as the different Google platforms: Android on phones, Android on tablets, TV, Chrome, etc.
Though typically I disagree with what he has to say John Gruber of daring fireball seems to think the same way I do:
"If there’s a hitch, it’s that Google seems to be promoting this as a cross-platform design framework — a way to design just one interface for both iOS and Android. Google’s own apps for iOS already feel like weird moon man apps; now they’re encouraging third-party developers to follow their style rather than iOS’s."
"The design team at Google felt the need to come up with a more coherent look and feel that could be applied across all of its products, from Android to Chrome OS to the web."