VoIP apps built against the iOS 9 SDK and earlier can still run in the background all the time, but we know WhatsApp and Facebook Messenger have used iOS SDK 10

VoIP apps built against the iOS 9 SDK and earlier can still run in the background all the time, but we know WhatsApp and Facebook Messenger have used iOS SDK 10 or higher since 2016 because they introduced support for CallKik back then which requires that version. Also, the current version of their apps only support iOS 9 and newer and PushKit has been available since 8. As far as I can tell, the media coverage is just misleading in a way that pushes their existing narratives about Facebook and Apple.