"The new Google Play app option will initially be released to select publishers for quality control and feedback. The Pixel Mags' developer team is eager to maximize the app's benefits and is looking forward to its broad release."
only appears on certain devices. I don't see it on my Samsung or Kindle but do see it on a generic Android device I have. It does not appear to be something new, however. Here are two links for it via the internet. The first says it is not available in my country. The second is a cached version which provides a little more info.
Market Data 
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