Facebook has literally told courts they can't decrypt WhatApp traffic. I wonder if that court case in Brazil is still pending.
By comparison, no one ever said "There's no way Google could read my search terms".
A more accurate comparison would be regarding Allo.
No, WatsApp didn't get informed of what URL you entered on the message. The site owner gets a notice, as does the user's ISP, and a lot of people in between. But WatsApp can not tell what URL was typed.
So they are in the clear legally, but morally, its still dubious to do that given its effectively disclosing what is often a substantial portion of the conversation.
And, transmitting an URL usually has no use beyond accessing it. They are doing what the user expects, it's just lacking some communication and power-user tools to override the default behavior.
Let us just say there are certain things that can cause legal complications merely accessing it and not reporting it is technically still a crime.
http://www.stf.jus.br/portal/processo/verProcessoAndamento.a...
Yeah this is a much bigger deal, for sure, as it's a messaging app - just pointing out similar case in a different application.