Luckily all of this will be illegal in the EU thanks to the Digital Services Act, developers will have the right to know the exact reason for a rejection, and Google will need to provide real human support.
I'm sure they'll manage the process so that it so that it's a powerless human reading an AI's decision back to you. There's no way to legislate wanting to do a good job.
there are many completely valid and completely unactionable reasons for rejecting people. Yes this might make it a bit better but it's very hard to make someone who doesn't care about helping you help you. Even regulation can just make them do the minimum.
What I'm hearing is there's a hell of a European market to cater to USA and other regions to host apps, and then play hardball in getting real answers.