This is the story that Google wants you to believe by fast following Apple with pricing changes. They want to demonstrate that Apple has pricing power to regulators (just my theory). The reality is that Apple and Google are in competition, and if Google actually innovated on business model the way they do with every other aspect of their business, it would actually drive the app store fees down for Apple. Microsoft has tried to do this [1] but they don't have enough market power to move the needle.
I expect that developers for the Play store and App store are two sets with a big overlap