There is no stock iOS. There is only the Apple-provided iOS which you can't see the code and thus you can't actually check for anything.
On WhatApp: "Depending on the request WhatsApp’s response may include, if available, basic subscriber information (such as their name, service start date, last seen date, IP address, device type, and email address), and account information (such as a user’s "about" information, profile photos, group information and contacts list). In the ordinary course of providing its service, WhatsApp does not store message logs once the messages are delivered or transaction logs of such delivered messages. In order to comply with a valid legal request, such as a valid Pen Register Trap and Trace Order in the United States, WhatsApp may start collecting message logs and call logs for a particular user indicating who the communication was to or from, the time it was transmitted and from which IP address, and the type of communication (such as a text or call)."
https://faq.whatsapp.com/808280033839222
Yeah “stock” iOS is the version from Apple. I was trying to convey the additional optional security features that put it above all versions of Android, except Graphene.
WhatsApp is a third party app, created in china, purchased by Facebook. The real answer is don’t use it. But the danger of using WhatsApp is the same between Android and iOS. Again I’m trying to point out Graphene stands on its own here.
Cybersec researchers work pretty hard to breach iOS and their work is in the open, even if the public can’t look at the iOS source code.
Oddbean new post about login | logout 
