Shouldn't the developer have known this through reading the rules of the store BEFORE he/she developer the app? If you can't be bothered to do due diligence before making such a big business decision you aren't equipped to run a business.
This is exactly the process Google implicitly wants to have happen, its what we all want to have happen. Google just fumbled
And when you're running a business that's an incredibly stupid thing to do.
Perhaps the developer did do their due dilligence and saw that Google is (supposedly) OK with it.
He mentions it's a 'similar' process. Maybe there is a crucial difference in the way they are handling things. Hard to tell though as he doesn't mention what the other app is. Still my point stands. If you are breaking a rule because someone else has got away with it you are taking a big risk.
Don't like the rules? Don't publish on the play store and let people download the app from you website. It's perfectly doable.
Moreover, an official warning was issued more than an year ago reminding play store developers that all IAP should go thought the play store AND more recently, another famous app with more than 150000 users was removed for using PayPal for payment.
Edit: copying a comment from reddit: Go to a store and put your homemade apple pies on their shelves with a PayPal QR code and see if that store too becomes "unfair".
1)The "Play Store" is, like the name says, a store, just like every single store is a distribution channel.
2)While I understand that for some it may look unfair, a contract is a contract, you cannot sign and then ignore the rules of a contract because it's "unfair". You just don't sign it.
3)On iOS the app will not have been accepted in the first place and maybe (I'm just supposing) the developer didn't want to buy a mac, buy an iPhone, learn objective c and pay 100$ a year to make the app for iOS. :P