Solved
[ios] Icon shown in 'home button' screen not correct
It still shows the default Xamarin icon. Discovered on release version.
2 replies
Someone with a similar problem:
https://stackoverflow.com/questions/61895597/xamarin-forms-ios-wrong-task-icon
they said it just... went away.
Still happening on release version. However, like the above post, after restarting the iPhone it just goes away. Seems to be a bug with Xamarin. I posted a ticket here - I don't think there's much else I can do about this.