What do restrictions for apps on the Play store have to do with walled garden vs open? If the block you from loading VR apps from outside the store, that would be a walled garden. The stores itself IMHO are very similar already.
Google would have better products if it had the focus and control of Apple. Google's products have suffered in the past from a short attention span and early abandonment, not to mention fragmentation. I'm glad Google is taking a page from Apple's playbook and paying more attention to quality control.