Here is an issue that I ran into yesterday with “Sign in with Apple”. I suspect I’m not alone in that situation.
The excellent website building tool, Universe, came out with an update that introduces Sign-in with Apple. After updating the application on my iPad, I launch the app. I’m welcomed with a sign-in screen. The Sign-in with Apple option is prominently displayed. I tap on it. I’m then presented with the typical panel to decide if I expose my real email address and my real name. Now the troubles begin.
I’m already a user of Universe, which email did I use to create my initial account? I can’t remember. What if I choose the wrong one? I try one of my email address that I decided to reveal. Hit sign-in; after a few seconds of working progress, I’m met with welcome screen for new users. Duh. I’m trying to get back, to no avail.
This issue reveals a big flaw in Sign in with Apple: when you are already a user of a service, switching to the more secure sign-in option makes it hard to associate this login to your existing account. I ran into the same issue with most of the services where I tried to make the switch. I suspect this is hindering the adoption of an otherwise secure upgrade to traditional authentication service. Too bad.