What definition of contact details makes them not private?
Contact details (your phone number, email or address) are definitively private information, you should be the one that decides who gets them and who doesn't.
But it's not meant to be shared widely, for most people it's meant to be shared with consideration and/or permission.
Also, it's not just about "a desire not be interrupted by people you didn't agree to be interrupted by", it's about not having the data in the first place, for any reason, including tracking of any sorts.
Pre-internet/cell phone nearly everyone had their name/phone number/address in phone books. Libraries had tons of phone books. And you could pay for the operator to find/connect you to people as well.
Contact info being private is a relatively recent concept.
Contact details (your phone number, email or address) are definitively private information, you should be the one that decides who gets them and who doesn't.