Secondly, it's only available on networks you choose to allow this on.
I don't have any choice. If I give my friend my WiFi password, and he happens to be running a Windows 10 phone, suddenly my WiFi password is shared with all of his contacts. So now every time someone is over my house and asks for the WiFi I'll have to ask them if they currently own, or ever intend to own a windows phone. And then, assuming they understand the question, I have to sound like a paranoid asshole and say "no" if they answer in the affirmative. My other option is to rename mySSID to end in _optout and update all of my devices because Microsoft chose to implement a ludicrous, criminally insecure, "feature"?
Third, yes, your wifi passwords are being backed up to make it easier when you migrate devices - Apple, Google and Microsoft all do this on your mobile devices. This isn't new!
Apple's encryption is end-to-end. They do not hold the encryption keys and thus can't share your passwords with anyone: Even if some brain dead middle manager had the idea to clone this feature, it would be impossible for them to implement without totally changing their security model.