The service sort of implies otherwise. If it's a phone number they'll get texts and iMessages. If they're using the feature that forwards iMessages to an AppleID the SIM must be in an iPhone, and I hardly think they'd reply to every SMS from a single iPhone.
The easier answer is that the screenshots are faked and not actually sent through the service; they probably just renamed a real contact who happened to have an iPhone 'Jarvis' for the purpose of making screenshots.
All the screenshots have timestamps a few minutes apart showing a plugged-in iPhone with an increasing charge over the course of a few minutes.
