I don’t know the author, but in a typical company, a project that is meant to work on iOS and Android will be dispatched to separate teams.
In this case, the author might be part of the Android team, instructed to make Sign in with Apple work on Android, and they may not even be in the same physical location as the iOS team.
But, if he's at a company with the resources for 2+ mobile dev teams, surely he could convince his manager to purchase an iOS device? We have several drawers full of mobile devices for testing our web apps. Our mobile dev teams have their own piles of devices. It's a cost of doing business.
In this case, the author might be part of the Android team, instructed to make Sign in with Apple work on Android, and they may not even be in the same physical location as the iOS team.