Google are vile. Decisions like this should always be appealable to an independent tribunal, the way that employment disputes are.
I'd go so far as to suggest that app developers are de facto employees, on that note: a recent ruling in the UK against Uber suggests that those who rely on such platforms are entitled to protections. I'd suggest that could apply here, too.
In the UK we have a category of "worker" which is between self employed and employed. I strongly suspect the fact that google play is the sole marketplace for most apps has an effect that brings people into that definition. It is about whether or not a business is captive, and whether it relies entirely on one platform for its customers. These things are what got GMB their victory over Uber in the employment tribunal.
I'd go so far as to suggest that app developers are de facto employees, on that note: a recent ruling in the UK against Uber suggests that those who rely on such platforms are entitled to protections. I'd suggest that could apply here, too.