"I received email from two people who told me that Microsoft Edge enabled synching without warning or consent"
Sure because 2 people saying it "must be true", I use Microsoft Edge with with my Microsoft Account synched and Edge always asks me what I want to synch when I first login with my account + in Edge Synch options you have the option to "Reset Microsoft Edge data in the cloud".
Most likely those 2 people that mail him are the type of people that when first uses a browser dont read the messages that appear in the first setup and just click next, next, next...
